Classical Mechanics Answers

A ball moving along the x axis bounces elastically off a horizontal wall that runs in along y-axis.
Suppose the momentum of the ball has also a y-component before it collides elastically with the wall. After the collision the x-component of the ball's momentum changes but its y-component does not. If then the momentum of the ball before the collision is P=Pxi+Pyj, what is its momentum after the collision.

A ball moving along the x axis bounces elastically off a horizontal wall that runs in along y-axis.
The magnitude of the momentum of the ball is the same before and after the collision.
Explain how we can conclude that the ball-wall system is closed but not isolated.

A ball moving along the x axis bounces elastically off a horizontal wall that runs in along y-axis.
The magnitude of the momentum of the ball is the same before and after the collision.
If the x-component of the ball's momentum is Px before the collision with with the wall, what is it after collision?

If a small ball is moving at constant velocity, v, in the plane of the paper. If there are no external forces acting on the ball, describe the path of the ball in terms of the position,r, and velocity, v, of the ball.

If after being thrown, the plastic cone starts falling with velocity of 9.8m/s, what would be its kinetic energy?

A flywheel has a moment of inertia of 1.6 × 10−3 kg.m2
. When a constant torque is
applied, it reaches an angular velocity of 1200 rev/min in 15 s. Assuming it started from
rest, find:
i) the angular acceleration
ii) the unbalanced torque applied
iii) the angle turned through 15 s
iv) the work done on the flywheel by the torque

A flywheel has a moment of inertia of 1.6 × 10−3 kg.m2. When a constant torque is applied, it reaches an angular velocity of 1200 rev/min in 15 s. Assuming it started from rest, find: i) the angular acceleration ii) the unbalanced torque applied iii) the angle turned through 15 s iv) the work done on the flywheel by the torque

Scuba divers are admonished not to rise faster than their air bubbles when rising to the surface. This rule helps them avoid the rapid pressure changes that cause the bends. Air bubbles of 1.0 mm radius are rising from a scuba diver to the surface of the sea. Assume a water temperature of 20 'C.

a) If the viscosity of the water is 1.0 x 10-3 Pas, what is the terminal velocity of the bubbles?

b) What is the largest rate of pressure change tolerable for the diver according to this rule?

At any angular speed, a certain uniform solid sphere of diameter D has half as much rotational kinetic energy as a certain uniform thin-walled hollow sphere of the same diameter when both are spinning about an axis through their centers. If the mass of the solid sphere is M, the mass of the hollow sphere is
1 : 3/5 M.
2 : 5/3 M.
3 : 5/6 M.
4 : 6/5 M.
5 : 2 M.

A bicycle is traveling north at 5.0 m/s. The mass of the wheel, 2.0 kg, is uniformly distributed along the rim, which has a radius of 20 cm. What are the magnitude and direction of the angular momentum of the wheel about its axle?
1 : 2.0 kg • m2/s towards the west
2 : 5.0 kg • m2/s vertically upwards
3 : 2.0 kg • m2/s towards the east
4 : 5.0 kg • m2/s towards the east
5 : 5.0 kg • m2/s towards the west