1. Can the velocity of an object be zero at the same instant its acceleration is not zero? Give an example.
2. Compare the acceleration of a car that speeds up from 60 to 70 km/hr in 5 seconds with a cyclist who accelerates from rest to 10 km/hr also in 5 seconds.
3. At an average speed of 15km/hr. how far will a bicyclist travel in 4.5 hours.
4. The distance from New York to Chicago is 1400km. How long will this trip take if you average 90km/hr.
5. 55 mph is how many (a) km/hr, (b) m/s, © ft/s?
6. What is the acceleration of a car that travels on a straight road from rest to 80km/hr in 8 seconds?
7. A stone is dropped from a cliff and is seen to hit the ground 4.5s later. How high was the cliff?
8. A modern version of one of Galileo's experiments is performed by dropping a golf ball from the observation deck of the Empire State Building. The measured position at various times are as follows:
|t, time (sec)||0||2||4||6||8|
|s, distance (m)||0||19.7||78.5||176||315|
Now, if the position s of a uniformly accelerating object is measured at various times t, the acceleration can be computed from adjacent points by:
where )s and )t2 are the differences between positions and squares of times. (a) compute four values of g using the above formula. (b) find the average of the experimental values of g and the probable value?
9. An airplane is flying horizontally, parallel to the ground with a velocity of 500 km/hr. The airplane is 2000 meters from the ground. A relief package is dropped from the plane.10. Aristotle said that the speed with which the object fall is constant. However, Galileo later claimed that objects fall with constant acceleration. Suggest a way that an experimenter might try to determine which of these claims is correct. Write what specific experimental equipment (such as stopwatch) one might use and briefly describe the experiment.a. Draw the path of the package (neglect air resistance)
b. How much time will pass between the drop of the package and the time it hits the ground.
c. Where will be the plane when the package will hit the ground?:
11. Bicyclists travel at a uniform speed of 10 mph toward each other. At the moment when they are 20 miles apart, a bumble bee flies from the front wheel of one of the bikes at a uniform speed of 25 mph directly to the wheel of the other bike. It touches it and turns around in a negligibly short time and returns at the same speed to the first bike, whereupon it touches the wheel and instantaneously turns around and repeats the back-and-forth trip over and over again - successive trips becoming shorter and shorter until the bikes collide and squash the unfortunate bee between the front wheels. What was the total mileage of the bee in its many back-and-forth trips from the time the bike were 20 miles apart until its hapless end?
12. A motorist in a car moving at 50 miles/hr sees an obstacle in the road 300 feet ahead. With a reaction time of 2 seconds he slams on his brakes. What constant (negative) acceleration is required to avoid collision? What total time has elapsed?
13. The B44 bus is approaching Brooklyn College at 144 inches per second. A student in the bus is facing forward and walking forward in the bus with a speed of 36 inches per second relative to the seats and things in the bus. The student is also eating a Submarine sandwich which is entering his mouth at 2 inches per second (fast). An ant on the submarine is running to the end of the sandwich, away from the person’s mouth. The distance between the ant and the end of the sandwich toward which it is running is closing at 1 inch per second. How fast is the ant approaching the College?, Explain!
Convert your answer from inch/s to miles per hour.
14. A marble with speed 1m/s rolls of the edge of a table 1m high. How long does it take to drop to the floor? How far, horizontally, from the table edge does the marble strikes the floor?
15. The following table shows the displacement of a car from its starting point as a function of time.
b. Plot approximately the velocity as a function of time.
16. A car that can decelerate at a maximal rate of 3.0 m/s2 is moving at 48km/hr (30mi/h) when the driver sees a stationary car in her lane, 40 m ahead of her. A third car approaching from the opposite direction makes it impossible for her to pass the stopped car. Assuming that the driver’s reaction time is such that she can apply the brakes 0.10 s after seeing the stopped car, can she avoid a collision? If so, by how much will she stop short of the second car?
17. A passenger in a train moving at a constant velocity drops a ball. a. How does the passenger see the ball move? (b) How does an observer on the ground see it move?
Choose the one alternative that best completes the statement or answers the question.1. The average speed of a horse that gallops a distance of 10 kilometers in a time of 30 minutes is:Your Answer?A. 10 km/h
B. 20 km/h
C. 30 km/h
D. More than 30 km/h2. What is the acceleration of a car that maintains a constant velocity of 100km/h for 10 seconds:Your Answer?A. 0
B. 10 km/h/s
C. 10 m/s2
D. 1000 km/h/s3. The gain in speed each second for a freely-falling object (g = 9.80 m/s2) is:A. 0
B. 5 m/s
C. 10 m/s
D. 20 m/s
E. Depends on the initial speed.
Your Answer?4. If an object falls with a constant acceleration, the velocity of the object must be:Your Answer?A. Be constant also.
B. Continually change by the same amount each second.
C. Continually change by varying amounts depending on its speed.
D. Continually decrease.
E. None of these.5. If a baseball being thrown goes from zero to 30 m/s in 0.1 second, what is the average acceleration?Your Answer?A. 3 m/s2
B. 30 m/s2
C. 300 m/s2
D. 3000 m/s2
E. None of these6. A bus is moving at 10 m/s. If you walk at 1 m/s down the aisle in the direction the bus is moving, your speed relative to the ground is:Your Answer?A. 0 m/s
B. 9 m/s
C. 10 m/s
D. 11 m/s7. A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, its vertical component of velocityYour Answer?A. Increases
B. Remains unchanged
C. Decreases8. A projectile is launched vertically at 50 m/s. If air resistance is negligible, its speed upon returning to the ground is:Your Answer?A. Less than 50 m/s
B. 50 m/s
C. More than 50 m/s9. A bullet fired horizontally hits the ground in 0.5 seconds. If it had been fired with twice the speed in the same direction, it would have hit the ground inYour Answer?A. Less than 0.5 s
B. More than 0.5 s
C. 0.5 s10. A ball player wishes to determine pitching speed by throwing a ball horizontally from an elevation of 5 m above the ground. The player sees the ball land 20 m down range. What is the player’s pitching speed?Your Answer?A. 5 m/s
B. 10 m/s
C. 20 m/s
D. 25 m/s
E. None of these
11. An airplane flies at 40 m/s at an altitude of 50 meters. The pilot drops a heavy package which falls and strikes the ground. Where, approximately, does the package land relative to its new position?Your Answer?A. Beneath the plane
B. 400 m behind the plane
C. 500 m behind the plane
D. More than 500 m behind the plane
E. None of these
NEWTON'S LAWS:1. What is the net force being exerted on a 1400-kg car accelerating at 3.5 m/s2?
2. Explain, using Newton's third law, why when you walk on a log floating in water, the log moves backward as you move forward. Draw a diagram of the log and a person walking on it, and show the motion of each.
3. What net force is needed to bring a 1000kg car to rest from 25m/s (90km/hr) in 5.0sec.
4. What is your mass in kilograms and your weight in Newtons?
5. How much would you weigh on the moon? Compare to your weight on earth (use the mass and radius of the earth and the moon in the units page in your "survival pages")
6. What is the weight of a 70-kg astronaut (a) on earth, (b) on the moon where g= 1.7m/s2, (c) on Venus where g = 8.7 m/s2, (d) in outer space?
7. A man pushes on a lawn mower at an angle of 450 to the ground with a force of 50 N. What is the component of this force in the horizontal direction? (you don't need trigonometry for this)
8. Calculate the force required to give an automobile of 1000-kg mass an acceleration of 5m/sec2. If that same force were applied to a 2500kg car, what acceleration would result?
9. A hypothetical planet has a mass of 2.2 times that of earth, but the same radius. What is g near its surface? what will be your weight on the surface of this planet.
10. How high above the Earth’s surface would a person of weight 250 lb have to go to "lose" 50 lb of weight.
11. Calculate the force required to give an automobile of 1000-kg mass an acceleration of 5m/sec2. If that same force were applied to a 2500kg car, what acceleration would result?12. A racing car travels around a curve of radius 30 meters at a speed of 30 m/s. What is the centripetal acceleration? Express the answer in "g"; that is how many times larger than the acceleration due to gravity, g=9.8 m/s2, is this?
Why does a car tend to skid on an icy curve?
13. The stevedore is loading 100-pound drums on a truck by rolling them up a ramp. The truck bed is 3 feet above the street and the ramp is 6 feet long. How much force must she exert on the drums as she goes up the ramp? Explain!
__________ 200 lb, _______100 lb, ______50lb, _________10 lb __________ Can’t say
14. A force acts on a 2-kg mass and gives it an acceleration of 3 m/s2. What acceleration is produced by the same force when acting on a mass of (a) 1kg? (b) 4kg? © How large is the force?
WORK AND ENERGY
1. In which case is more work done: when a 50-kg bag of groceries is lifted 50 cm or when a 50-kg crate is pushed 2 m across the floor with a force of 50 N?
2. Why do the stopping distance of a car when the brakes are applied increase with the square of the car's speed?
3. A car rolls from rest down a hill with no friction. At the bottom of the hill its speed is 10m/s. How high is the hill?
4. A driver's examination has the following question: " A car with speed 30 mi/hr hits head-on with another moving 40mi/hr. The damage will be the same as a car hitting a solid wall at (check one and explain) __________ 70mi/hr, _______10mi/hr, ______50mi/hr, _________35mi/hr." Assume that all kinetic energy goes into physical damage.
5. Describe all the energy transformations that take place when you throw a ball into the air, when the ball reaches its maximum height and descends, and finally, when you catch it.6. A boy throws a 0.15kg stone from the top of a 20-m cliff with a speed of 15 m/s. Find the kinetic energy and the speed when the stone lands in the river below?
7. An advertisement claims that a certain 1200-kg car can accelerate from rest to a speed of 25 m/s in a time of 8 s. What average power must the motor produce in order to cause the acceleration? Ignore friction.
8. Water falls 100 m over a dam at a rate of 15,000kg/s. How many megawatts of electric power could be produced by a power plant using this energy?.9. A 400-lb load of bricks is to be lifted to the top of a scaffold 28ft high. How much work has to be done against gravity?
10. A pump lifts water from a lake to a large tank 20 m above the lake. How much work does the pump do as it transfers 5m3 of water to the tank? One cubic meter of water has a mass of 1000kg.
11. What is the law of conservation of mechanical energy? Under what conditions it applies?
Multiple Choice1. Your weight isA. Actually your mass
B. The gravitational attraction between you and the earth
C. A property of mechanical equilibrium
D. All of these
E. None of these2. Compared to the mass of certain object on earth, the mass of the same object on the moon isA. Less
C. The same3. A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity isA. 0 N
B. Equal to the weight of the puck
C. The weight of the puck divided by the mass of the puck
D. The mass of the puck divided by 9.8 m/s2
E. None of these4. In which case would you have a largest mass of gold? If your chunk of gold weighed 1N onA. Moon
C. Jupiter5. An object is pulled northward with a force of 10 N and southward with a force of 15 N. The magnitude of the net force on the object is:A. 0 N
B. 5 N
C. 10 N
D. 15 N
E. None of the above6. Suppose you’re coasting on level ground in a car at 60 km/h and apply the brake until you slow to 40 km/h. When you suddenly release the brake, the car tends toA. Momentarily regain its higher initial speed
B. Continue moving at 40 km/h in the absence of forces
C. Decrease in speed whether or not other forces act7. A car has a mass of 1000 kg and accelerates at 2 m/s2. What is the magnitude of the force exerted on the car?A. 500 N
B. 1000 N
C. 1500 N
D. 2000 N
E. None of the above8. A bag of groceries has a mass of 10 kilograms and a weight of aboutA. 1 N
B. 10 N
C. 100 N
D. 1000 N
E. More than 1000 N9. The force exerted on the tires of a car to directly accelerate it along a road is exerted by theA. Engine
F. None of these.10. A car traveling at 100 km/hr strikes an unfortunate bug and splatters it. The force of impact is greater on theA. Bug
C. The same for both11. What is the force of gravity on a 500N woman standing on the earth’s surface:A. 50N
E. None of these11. Consider two planets in space that gravitationally attract each other. If the masses of both planeta is doubled, and the distance between them is also doubled, then the force between them isA. One quarter
B. Half as much
C. Twice as much
D. Four times as much
E. None of these12. A woman who weighs 400 N stands on top of a very tall ladder so she is one earth radius above the earth’s surface. How much would she weigh there?A. Zero
B. 100 N
C. 200 N
D. 400 N
E. None of these13. The planet Jupiter is about 300 times as massive as earth, yet on its surface you would weigh only about 3 time as much. This is becauseA. Your mass is 100 times less on Jupiter
B. Jupiter is significantly farther from the sun
C. Jupiter’s radius is 10 times the earth’s radius
D. You are 100 times more weightless there
E. None of these14. If a job is done slowly, while an identical job is done quickly. Both jobs require the same amount of work but different amount ofA. Energy
C. Both of these none of these15. Exert 100 J in 50 s and your power output isA. 1/4 W
B. ½ W
C. 2 W
D. 4 W
E. More than 4 W.16. In the figure below - the bead has maximum speed at point
E17. The bead has maximum potential energy at point:A.
E18. No work is done by gravity on a bowling ball that rolls along a bowling alley becauseA. No force acts on the ball
B. No distance is covered by the ball
C. The force on the ball is at right angle to the balls motion
D. No potential energy is converted to kinetic energy
E. Its kinetic energy is constant.19. A car moving at 50 km/hr skids 20 m with locked brakes. How far will the car skid with locked brakes if it is traveling 150 km/hr.A. 20 m
B. 60 m
C. 90 m
D. 120 m
E. 180 m
Energy Heat and Temperature
1. Room temperature is often defined as 68°F, What temperature is this on the Celsius scale? on the absolute scale?
2. In an alcohol-in-glass thermometer, the alcohol column has length 12.4cm at 0.0°C and length of 21.3 cm at 100.0°C. What is the temperature if the column has length (a) 15.1 cm (b) 22.95 cm?
3. If a gas is compressed to one-fifth its original volume but the temperature is kept constant, what happens to the pressure?
4. A gas is maintained at constant temperature. If the pressure on the gas is doubled, the volume is changed by what factor?
5. If the pressure on a gas is tripled, what happens to the volume if the temperature is kept constant?
6. How much heat (in Joules) is required to raise the temperature of 2.0kg of water from 0°C to 20°C. (specific heat of water = 4180Joule/kg.°C)
7. How many kilocalories of heat are generated when the brakes are used to bring a 1400-kg car to rest from a speed of 80km/hr ?
8. Calculate the maximum efficiency of a steam engine that operates between 500°C and 250°C.
9. A heat engine produces 9500J of heat while performing 2500J of useful work. What is the efficiency of this engine?
10. Describe all the energy transformations that take place when you throw a ball into the air, when the ball reaches its maximum height and descends, and finally, when you catch it.
11. The chemical potential energy in a certain amount of gasoline is converted to kinetic energy in a car that increases its speed from 0 mph to 32 mph. To pass another car the driver accelerates to 64 mph. Compared to the energy required to go from 0 to 32 mph, the energy required to go from 32 mph to 64 mph is:
Half_____, Equal______, Twice______, Three times, Four times______
12. A water heater can generate 10,000 kcal/hr. How much water can it heat from 10oC to 50oC per hour. (specific heat of water = 1Kcal/kg.°C).
13. If 5 m3 of gas initially at atmospheric pressure and 0 oC is placed under pressure of 5 atm, the temperature of the gas rises to 25oC. What is the volume.
14. The oceans in the tropics have a surface temperature of about 25 0C whereas below in the depths the temperature is about 50C. The possibility of building heat engines to generate electricity using this temperature difference is being considered. What would be the maximum efficiency of such an engine? Why might such an engine be practical in spite its low efficiency? What adverse environmental effects might occur?
15. Water falls 100 m over a dam at a rate of 15,000kg/s. How many megawatts of electric power could be produced by a power plant using this energy?.
1. The fact that desert sand is very hot during the day and very cold at night is evidence that sand has a
A. Low specific heat. B. High specific heat
2. Room temperature on the Kelvin scale is about
A. 100K B. 200K C. 300K D. 400K
3. A temperature difference of 10 degrees Celsius is also equal to a temperature difference of 10 on
A. Fahrenheit scale. B. Kelvin scale C. Both of these D. Neither
4. Aluminum has a specific heat capacity more than twice that of copper. Place equal masses
of aluminum and copper wire in a flame and the one undergo the fastest increase in temperature will be
A. Copper B. Aluminum C. Both the same
5. Compared to a giant iceberg, a hot cup of coffee has
A. More internal energy and higher temperature
B. Higher temperature but less internal energy
C. A greater specific heat and more internal energy
D. None of these
6. Heat energy is measured in units of
A. Joules B. calories C. both of these
7. A substance that heats up relatively quickly has
A. High specific heat B. low specific heat
8. Heat energy travels from an object with a high
A. Internal energy to an object with a low internal energy
B. Temperature to an object with a lower temperature
C. Both of these, for they say essentially the same thing
9. When you touch a cold piece of ice with your finger, energy flows
A. From your finger to the ice
B. From the ice to your finger
C. Actually, both ways
10. A substance can absorb heat energy by the process of
D. All of these.
11. Evaporation is a cooling process because
A. Heat is radiated during the process
B. Of conduction and convection
C. The more energetic molecules are able to escape the liquid
D. The temperature of the remaining liquid decreases
E. None of these
12. Evaporation is a cooling process and condensation is
A. Warming process
B. Cooling process also
13. We feel uncomfortly warm in a muggy day because water molecules are
A. Evaporating from our moist body
B. Condensing on our bodies
C. Preventing the evaporation from our moist bodies
14. The lowest temperature possible in nature is
A. 0 degrees C
B. -273 degrees C
14. It is possible to wholly convert a given amount of energy of heat energy to mecahnical energy
15. It is possible to wholly convert a given amount of mechanical energy into heat
16. The greater the difference in temperature between the input heat reservoir and output reservoir for a heat engine, the
A. Greater the efficiency
B. Less the efficiency
C. Neither, efficiency doesn’t depend on temperature difference
17. Systems that are left alone, tend to move toward a state of
A. Less entropy
B. More entropy
C. No entropy
18. Entropy measures
A . Temperature at constant pressure
B. Temperature as volume increases
19. Industrialization on earth eventually heats our surroundings to temperatures that are higher than usual, industrialization in space habitat using exclusively solar power eventually will thermally pollute the solar system
20. One hundred joules of heat is added to a system that performs 60 joules of work. The internal energy change in the system is
A. 0 J
B. 40 J
C. 60 J
D. 100 J
E. None of these
21. One hundred joules of heat is added to a system that performs 60 joules of work. The efficiency of this engine in converting heat to mechanical energy is
A. 0 %
B. 40 %
C. 60 %
D. 100 %
E. None of these
22. Two identical blocks of iron, one at 10 degrees C and the other at 20 degrees C, are put in contact. Suppose the cooler block cools to 5 degrees C and the warmer block warms to 25 degrees C. This would violate the
A. 1st. Law of thermodynamics
B. 2nd. Law of thermodynamics
C. Both of these
D. Neither of these
23. The amount of energy ultimately converted to heath by a light bulb is
A . 15 %
B. 30 %
C. 45 %
D. 60 %
E. 100 %
24. The ideal efficiency for a heat engine operating between temperatures of 2700K and 300K is
A. 10 %
B. 24 %
C. 80 %
D. 89 %
E. None of these
25. The ideal efficiency for a heat engine operating between temperatures of 227C and 27C is
A. 20 %
B. 25 %
C. 40 %
D. 88 %
E. None of these
26. A container of air is at atmospheric pressure and 27 degrees C. To double the pressure in the container, it should be heated to
A. 54 degrees C
B. 300 degrees C
C. 327 degrees C
D. 600 degrees C
E. None of these
27. When a gas container is squeezed to half its volume and the temperature remains the same, the gas pressure
D. Remains the same
ENERGY, ELECTROMAGNETIC RADIATION
1. What is the frequency of a light wave whose wavelength is 6000Å?
2. What is 8max for a black body at a temperature of 300 oK and 5800oK?
3. Explain the green house effect and provide two examples.
4. What is the solar constant and suggest a way to calculate it from first principles.
5. Outline an approximate way to calculate the average temperature on the surface of the earth.
6. Suggest ways in which human intervention can modify the average temperature.
7. List some possible consequences of changes in the earth's average temperature.
1. If the sun were to disappear right now, we wouldn’t know about it for 8 minutes because it takes 8 minutes
A. For the sun to disappear
B. To operate receiving equipment in the dark
C. For light to travel from the sun to earth
D. All of these
E. None of these
2. What is the wavelength of an electromagnetic wave that has a frequency of 1 hertz
A. Less than 1 m
B. More than 1 m
3. Greenhouse effect means:
A. Passing through solar radiation and trapping infrared radiation.
B. Trapping humidity.
B. Tropical conditions suitable for forest growth
D. Trapping solar radiation
4. To calculate the average temperature on earth we need to know:
A. The solar constant
B. The radius of the earth
C. The percentage of radiation reflected by the atmosphere
D. All of the above
E. None of the above