Collected Problems for Test 3
Problem #18 (Due 3/21 Wednesday by 2:00 p.m.)
#6, page 230
Problem #19 (Due 3/22 Thursday by 2:00 p.m.)
A net force Fnet = A + Bt2 in the +x direction is applied to a girl on roller skates. The girl has mass m. The force starts at t1 = 0 and continures until t = t2.
a) What is the impulse of the force?
b) If the girl is initially at rest, what is her speed at t2?
Problem #20 (Due 3/23 Friday by 2:00 p.m.)
A movie stuntman of mass 80.0 kg stand on a ledge 5.0 m above the floor. Grabbing a rope attached to a chandelier, he swings down to grapple with the movie's villain (mass 70.0 kg), who is standing directly under the chandelier. Assume the stuntman's center of mass moves downward 5.0 m and he releases the rope just as he reaches the villain.
a) With what speed to the entwined foes start to slide across the floor?
b) If the coefficient of kinetic friction of their bodies with the floor is 0.250, how far do they slide?
Problem #21 (Due 3/28 Wednesday by 2:00 p.m.)
A 237 g air-track glider moving at 0.80 m/s on a 2.4 m long air track collides elastically with a 513 g glider at rest in the middle of the track. The end of the track over which the struck glider moves is not level, but slants upward at an angle of 0.70o with respect to the horizontal. Will the glider reach the end of the track? Neglect the length of the gliders.
*Make sure you draw your before and after picture for the collision part and don't use any "magic" formulas.
Problem #22 (Due 3/29 Thursday by 2:00 p.m.)
Two cards collide at an intersection. Car A, with a mass of 2020 kg, is going from west to east, while car B, of mass 1510 kg, is going from north to south at 15 m/s. As a result of this collision, the two cars stick together and move as one afterwards. In your role as an expert witness, you inspect the scene and determine that, after the collision, the cars moves at an angle of 65o south of east from the point of impact.
a. How fast were the cars moving just after the collision?
b. How fast was car A going just before the collision?
Problem #23 (Due 3/30 Friday by 2:00 p.m.)
A flywheel having constant angular acceleration requires 4.00 s to rotate through 162 rad. Its angular velocity at the end of this time is 108 rad/s.
a) Find the angular velocity at the beginning of the 4.00 s interval.
b) Find the angular acceleration of the flywheel.
Problem #24 (Due 4/4 Wednesday by 2:00 p.m.)
A cylinder with radius R and mass M has density that increases linearly with distance r from the cylinder axis, 
(roe = alpha x r), where 
(alpha) is a positive constant.
a) Calculate the moment of inertia of the cylinder about a longitudinal axis through its center in terms of M and R.
b) Is your answer greater or smaller than the moment of inertia of a cylinder of the same mass and radius but of uniform density? Explain why this result makes qualitative sense.
Problem #25 (Due 4/5 Thursday by 2:00 p.m.)
A large 16.0 kg roll of paper with radius R = 18.0 cm rests against the wall and is held in place by a bracket attached to a rod through the center of the roll. The rod turns without friction in the bracket, and the moment of inertia of the paper and rod about the axis is 0.260 kg.m2. The other end of the bracket is attached by a frictionless hinge to the wall such that the bracket makes an angle of 30.0o with the wall. The coefficient of kinetic friction between the appear and the wall is 0.25. A constant vertical force F = 40.0 N is applied to the paper, and the paper unrolls.
a) What is the magnitude of the force that the rod exerts on the paper as it unrolls?
b) What is the angular acceleration of the roll?
Problem #26 (Due 4/6 Friday by 2:00 p.m.)
A solid, uniform ball rolls without slipping up a hill as shown. Initially, at the bottom of the hill, the ball has a linear speed of 25.0 m/s. At the top of the 28.0 m high hill it launches off of a 30.0o slope into the air.
a) How far from the foot of the cliff does the ball land?
b) How fast is the ball moving just before it lands?
c) Compare your answer from b) with the initial linear speed of 25.0 m/s. Does you answer make sense? Explain.
