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Physics 250
Exam II
Fall 2003
Name:______________________
Part I
Choose the best answer
Constants:
g = 9.81 m/s2
Multiple Choice
(4 points each)
___ 1. A passenger on a Ferris wheel is undergoing uniform circular motion. The
passenger “feels heaviest” when moving
(A) at the top of the circle
(B) downward, halfway between the top and the bottom of the circle
(C) upwards, halfway between the top and the bottom of the circle
(D) at the bottom of the circle
(E) towards the cotton candy vendor
___ 2. 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.
___ 3. If the orbital distance of the moon from the earth were larger, then
(A) the force of attraction between the earth and the moon would be smaller.
(B) the centripetal acceleration of the moon would be less.
(C) the period of the moon’s orbit would be larger (the “month” would be longer)
(D) the orbital speed of the moon would be faster
(E) all of the above
___ 4. 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.
___ 5. 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.
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Physics 250
Exam II
Fall 2003
___ 6. A baseball bat strikes a pitched baseball and sends it flying. Which has the greater magnitude of
momentum change during the impact?
(A) the ball.
(B) the bat.
(C) they both have the same magnitude momentum change.
(D) it depends upon the speed of the ball.
(E) it depends upon the team, the fans and the umpire.
___ 7. If you are riding in a cart on frictionless, straight tracks and you take a brick and throw it out the rear, then
(A) the cart will speed up.
(B) the cart will slow down.
(C) the cart will continue moving at the same speed.
(D) the cart will stop.
(E) the cart burst into flames.
___ 8. 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.
___ 9. Torque () seems to play a similar role in rotation to (i.e. is analogous to)
(A) Force (F) in linear motion.
(B) Momentum (p) in linear motion.
(C) Mass (m) in rotational motion
(D) linear analogue of .
(E) linear analogue of Angular Momentum (L) in rotational motion.
___ 10. The Great Race: A solid disk and a hoop of the same mass and radius are released from rest at the top of
an inclined plane (as in the lecture demonstration). The object which has the greatest total kinetic energy
at the bottom of the plane (after rolling down from the same height h) is the
(A) hoop.
(B) disk.
(C) both have the same final KE.
(D) more information would be required to answer this question.
(E) neither, since an interdimensional wormhole will spontaneously open to annihilate both objects before
they reach the bottom.
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Physics 250
Exam II
Part II
Show your work! No work=no credit
Problems
Fall 2003
(15 points each)
1. Planet X has an artificial satellite of mass 500 kg in orbit about it with a period of 30 hours and an orbital
radius of 450000 km.
(A) What is the speed of the satellite?
(B) What is the radial acceleration of the satellite?
(C) What is the magnitude of the force keeping the satellite in orbit?
(D) What is the mass of Planet X?
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Physics 250
Exam II
Fall 2003
2. A 1500 kg car is coasting down a hill
(A) What is the change in the car’s kinetic energy as car’s speed increases from 5.00 m/s to 15.0 m/s?
(B) How much gravitational potential energy was used in speeding up the car?
(C) What was the change in height of the car as it coasted down the hill?
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Physics 250
Exam II
Fall 2003
3. A 30.0 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 momentum of the boy?
(C) What is the final momentum of the boy/sled (treated as a single object moving together) ?
(D) What is the final speed of the boy/sled?
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Physics 250
Exam II
Fall 2003
4. A torque of 500 N.m is applied to a disk initially at rest. The disk has a moment of inertia of 2 Kg.m2.
After 5 full rotations determine
(A) the angular acceleration of the disk,
(B) the final angular velocity (in rad/s) of the disk,
(C) the time required for the 5 full rotations, and
(D) the final rotational kinetic energy of the disk.
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