Physics 150 Exam Bank II Fall 1999

In general, the work done on an object may produce a change in (A) the object’s total energy. (B) the object’s potential energy only. (C) the object’s thermal energy only. (D) the object’s kinetic energy only. (E) the weather.

A rolling disk loses PE as it rolls down an inclined plane. Gravity is an example of (A) a dissipative force (B) a nonconservative force. (C) a conservative force. (D) a liberal force. (E) any of the above depending upon the reference height.

The net work done on an object (A) is equal to the change in the total energy of the object. (B) depends upon the path of the object if there are nonconservative forces acting on the object. (C) has unites of Joules. (D) all of the above.

A large mass collides elastically head on with a small mass which is initially at rest. The small mass (A) rebounds at a higher speed than the large mass, because energy an momentum are conserved. (B) sticks to the large mass, slowing it considerably because energy an momentum are conserved. (C) causes the large mass to rebound in the opposite direction. (D) spontaneously bursts into flame, engulfing the large mass and two adjacent multiple choice questions in a spectacular pyrotechnics display. (E) none of the above.

If the speed of a mass is doubled, then that mass’s (linear) kinetic energy (A) is quadrupled. (B) is doubled. (C) is unchanged. (D) a halved. (E) any of the above depending upon the initial kinetic energy height.

To keep a vehicle moving at a requires that the engine delivers a power P. The amount of work W done in a time T is (A) W = P /T. (B) W = 1/2 PT2. (C) W = P T. (D) W = T /P.

1 Physics 150 Exam Bank II Fall 1999 To keep a vehicle moving at a speed v requires that a force F be applied along the direction of motion. The power required to keep the vehicle moving is (A) 1/2 Fv2. (B) Fv2. (C) F/v. (D) Fv. (E) none of the above.

The work done in moving an object from point A to point B against a dissipative force (A) cannot be recovered by moving it from point B to point A. (B) depends upon the path the object takes moving from point A to point B. (C) cannot give rise to a potential energy.

A dropped pall loses PE as it falls. Gravity is an example of (A) a conservative force. (B) a nonconservative force. (C) a dissipative force. (D) momentum.

A mass attached to a spring gains PE as the spring is compressed. The force provided by the spring is an example of (A) a conservative force. (B) a nonconservative force. (C) a dissipative force. (D) momentum.

The work done in moving an object from point A to point B against a conservative force (A) can be recovered by moving it from point B to point A. a (B) does depend upon the path the object takes moving from point A to point B. (C) can not be written as a change in potential energy. (D) all of the above. (E) none of the above.

For the pendulum bob swings as shown at right: (A) at point (a) PE (potential energy) is minimum and KE (kinetic energy) is maximum while at point (b) PE is maximum and KE is minimum. a (B) at point (a) PE and KE are both minimum while at point (b) PE and KE b are both maximum. (C) at point (a) is PE maximum and KE is minimum while at point (b) PE is minimum and KE is maximum. (D) at point (a) PE and KE are both maximum while at point (b) PE and KE are both minimum. (E) none of the above.

2 Physics 150 Exam Bank II Fall 1999 When the velocity of an object is doubled, (A) its momentum is halved. (B) its potential energy is halved. (C) its kinetic energy is halved. (D) its acceleration is halved.

When the momentum of an object is doubled, (A) its acceleration goes up by a factor of four. (B) its momentum goes up by a factor of four. (C) its kinetic energy goes up by a factor of four. (D) its potential energy goes up by a factor of four.

When the velocity of an object is halved, (A) its momentum is halved. (B) its potential energy is halved. (C) its kinetic energy is halved. (D) its acceleration is halved.

When the velocity of an object is halved, (A) its momentum is quartered. (B) its potential energy is quartered. (C) its kinetic energy is quartered. (D) its acceleration is quartered.

An object that has momentum must also have (A) acceleration. (B) kinetic energy. (C) potential energy. (D) impulse.

In an inelastic collision (A) momentum is conserved but KE is not. (B) KE is conserved but momentum is not. (C) both KE and momentum are conserved. (D) neither KE nor momentum is conserved. (E) none of the above is always true.

In an elastic collision (A) momentum is conserved but KE is not. (B) KE is conserved but momentum is not. (C) both KE and momentum is conserved. (D) neither KE nor momentum is conserved. (E) none of the above is always true.

3 Physics 150 Exam Bank II Fall 1999 The centripetal force on a car rounding a curve on a level road is provided by (A) gravity. (B) friction between the tires and the road. (C) the torque applied to the steering wheel. (D) trick question, since the force and acceleration must be zero for motion with constant speed is zero.

The centripetal force on a mass on a string swung in a horizontal circle with constant speed is provided by (A) gravity. (B) the tension in string. (C) friction. (D) trick question, since the force and acceleration must be zero for motion with constant speed is zero.

The acceleration of an object undergoing uniform circular motion is constant in (A) magnitude only. (B) direction only. (C) both magnitude and direction. (D) neither magnitude nor direction. (E) none of the above is always true.

The speed of an object in uniform circular motion is constant. The centripetal force needed if the radius of the circle is doubled is (A) half as great as before. (B) twice as great as before. (C) exactly the same as before. (D) 4 times as great as before. (E) none of the above.

The speed of an object in uniform circular motion is doubled. The centripetal force needed if the radius of the circle remains the same is (A) half as great as before. (B) twice as great as before. (C) exactly the same as before. (D) 4 times as great as before.

The radius of the path of an object in uniform circular motion is halved (making a much tighter circle). The centripetal force needed if its speed remains the same is (A) half as great as before. (B) twice as great as before. (C) exactly the same as before. (D) 4 times as great as before. (E) none of the above.

4 Physics 150 Exam Bank II Fall 1999 The centripetal force necessary to keep the moon in orbit about the earth is provided by (A) inertia. (B) its rotation about its axis (C) the gravitational pull of the earth (D) the gravitational pull of the sun (E) none of the above.

The centripetal force necessary to keep the earth in orbit about the sun is provided by (A) inertia. (B) its rotation about its axis (C) the gravitational pull of the sun (D) the gravitational pull of the moon (E) none of the above.

By using Newton’s Law of Universal Gravitation and observing the orbital motion of , we weigh (i.e. determine the mass of) the . (A) moon about the earth, earth. (B) planets about the sun, sun. (C) Jupiter’s moons about Jupiter, Jupiter. (D) the stars of a galaxy about the center of the galaxy, galaxy. (E) all of the above.

2 Point Bonus: Does the orbital period of the planets get longer, shorter or remain the same, with increasing distance from the Sun?

5 Physics 150 Exam Bank II Fall 1999 Part II Problems Show all work. No work = no credit! (15 points each)

A mass is initially at rest when a 2.00 N force is applied. (A) What is the initial KE of the mass? (B) How much work is done on the mass by this force over a distance of 4.00 m? (C) What is the final KE of the mass?

A 20.0 kg mass is initially moving at 10.0 m/s when a 20.0 N force (braking) is applied, bringing it to rest. (A) What is the initial KE of the mass? (B) What is the final KE of the mass? (C) How much work is done on the object in bringing it to rest? (D) How far did the object travel before coming to rest?

A 5.00 kg mass is initially at rest when a 10.0 N force is applied. After it has traveled 10.0 m, determine (A) how much work is done on the mass, (B) what the final KE of the mass is and (C) what the final speed of the mass is.

A 100 kg physics professor initially moving at 3.00 m/s collides elastically head-on with a 2.00 kg garbage can initially at rest. (A) What is the initial momentum of the professor? (B) What is the final speed of the professor? (C) What is the final speed of the garbage can? (D) Was energy conserved in this collision? (Just answer Yes or No, no calculation should be necessary)

A .500 kg pigeon flies at 10.0 m/s until it flys into windshield of a truck travelling the opposite direction at 40.0 m/s driven by a “Hegin’s Shoot Protester”. The impact lasts 1.00 ms (.00100 s). (A) What is the initial momentum of the pigeon? (B) What is the final momentum of the pigeon (now travelling with the windshield)? (C) What is the impulse of the windshield upon the pigeon? (D) What is the average force exerted upon the pigeon by the windshield?

6 Physics 150 Exam Bank II Fall 1999 A 40.0 kg boy running at 5.00 m/s runs and jumps on a stationary 10.0 kg sled on a frozen lake. (A) What is the initial momentum of the sled? (B) What is the initial KE of the sled? (C) What is the initial momentum of the boy? (D) What is the initial KE of the boy? (E) What is the final momentum of the boy/sled (treated as a single object moving together) ? (F) What is the final speed of the boy/sled? (G) What is the final KE of the boy/sled?

An unknown mass is initially at rest when a 20.0 N force is applied. After it has traveled 4.0 m, determine (A) how much work is done on the mass, (B) the final KE of the mass.

A satellite is to have an orbit whose altitude is 500 km above the surface of the earth. (A) What is the speed of the satellite? (B) What is the period of the satellite’s orbit?

Physics 150 Exam Bank II Fall 1999 A string 1.00 m long is used to swing a 0.500 kg mass in a vertical circle. The speed of the mass at the top of the circle is 5.00 m/s. (A) What is the tension in the string at the top of the circle? (B) What is the KE of the mass at the top of the circle? (C) How much PE is lost going as the mass goes from the top of the circle to the bottom of the circle? (D) What is the KE of the mass at the bottom of the circle? (E) What is the speed of the mass at the bottom of the circle? (F) What is the tension in the string at the bottom of the circle?

8 Physics 150 Exam Bank II Fall 1999

Physics 150 Exam Bank II Fall 1999 A string 2.00 m long is used to swing a 0.200 kg mass in a vertical circle. The speed of the mass at the bottom of the circle is 12.00 m/s. (A) Draw a free-body diagram for the mass at the bottom of the circle (B) What is the tension in the string when the mass is at the bottom of the circle? (C) What is the KE of the mass at the bottom of the circle? (D) What is the increase in PE as the mass goes from the bottom of the circle to the top of the circle? (E) What is the KE of the mass at the top of the circle? (F) What is the speed of the mass at the top of the circle? (G) Draw a free-body diagram for the mass at the top of the circle (F) What is the tension in the string when the mass is at the top of the circle?

1 0 Physics 150 Exam Bank II Fall 1999

1 1 Physics 150 Exam Bank II Fall 1999 A motor which produces a power output of 20.0 kW is used to hoist an 400 kg bucket of concrete to the twentieth floor of a building under construction, a height of 100. m. (A) How much work is done lifting (against the force of gravity) the bucket the 100. m, assuming the bucket is at rest initially and after it reaches its destination? (B) How much time is required by the motor to perform this work?

A motor which produces a power output of 15.0 kW is used to hoist an 800 kg bucket of concrete to the twentieth floor of a building under construction, a height of 90.0 m. (A) How much work is done lifting the bucket the 90.0 m, assuming the bucket is at rest initially and after it reaches its destination? (B) How much time is required by the motor to perform this work?

A satellite is to have an orbital period of 12 h. (A) What is the radius of this orbit? (B) What is the altitude of this orbit?