SAMPLE TEST 2 SOLUTIONS
Problem 1 (10 points)
ANSWER: The heavy load applies a torque on you (clockwise). You need to lean backward to counterbalance that torque with the torque of your weight (counterclockwise).
ANSWER: The centripetal force is always perpendicular to the direction of motion. Only the component of the force in the direction of motion can do work. The centripetal force has no such component, so it can never do work.
ANSWER: It has both radial (centripetal) acceleration
If the angular velocity increases uniformly, then is constant, so the tangential acceleration does not change. The radial acceleration increases, because the angular velocity increases.
ANSWER: Air escapes from the balloon that carries momentum. By momentum conservation, the balloon acquires momentum which is exactly opposite to the momentum of the escaping air. Therefore, it flies in a direction which is opposite to the velocity of the escaping air.
ANSWER: The weight of the satellite is being used as a centripetal force.
In fact, the satellite is in a state of free fall because of its weight,
but never reaches the ground because all the weight can do is change the
direction of the tangential velocity.
Problem 2 (10 points)
A 20-g bullet traveling 300 m/s hits a 1.5-kg block of wood which is stationary on a frictionless surface and penetrates it. After the collision, the block moves with speed 0.8 m/s.
The momentum before the collision is
The impulse is
The kinetic energy before the collision is
Problem 3 (10 points)
You do work because the potential energy changes, so
In addition to the potential energy, you do work because of the friction,
which is
Problem 4 (10 points)
A 50-kg box is hanging from the ceiling as shown. Find the tension in the two chords supporting the box.
x-components:
Back to home page
Physics Department
401 Nielsen Physics Bldg., The University of Tennessee, Knoxville,
TN 37996-1200, U.S.A.