# A system of three objects

A system is composed of three objects with masses m, 5m and 6m. The coefficient of kinetic friction between the objects m, 5m and the surface is 0.5. Find the acceleration of the objects.

# Object, String & Elevator

An object of mass m is hanging by a string from the ceiling of an elevator. The elevator is moving upward, but slowing down.

What is the tension in the string?

a) zero
b) greater than mg
c) exactly mg
d) less than mg

# One Mass And Two Threads

A big mass is suspended from a thin thread. An identical thread is tied to the bottom of the mass. To break only the lower thread, one should:

a.
push upward on the lower thread.

b.
pull down on the lower thread with a quick, firm jerk.

c.
pull down on the lower thread with a gentle and slowly increasing force.

d.
All of these have the same effect.

e.
do none of these.

# An object slides down an inclined plane

An object slides down an inclined plane at a constant velocity. Find the coefficient of sliding friction if the plane is inclined at an angle of α degrees to the horizontal.

# A hockey player & referee

A 100 kg hockey player pushes a 80 kg referee with a force of 800N. Assuming they on a frictionless ice surface and the push lasts for 0.5 seconds, find the following: a) the acceleration experienced by each person b) the maximum velocity reached by each person c) do the resulting motions depend on which person instigated the pushing?   Continue reading

# Does the balance beam tip to the right, to the left, or does it remain unchanged?

You have a balance beam, the kind of scale that tips from one side to the other, depending on the weight on each side. On each side is a beaker, half-filled with water. The sides are in balance. Now, on the left side, you submerge a Ping-Pong ball suspended by a string. On the right side, you submerge a steel ball of the same volume as the Ping-Pong ball suspended from a crane.

You may ignore the mass of the strings.

Does the balance beam tip to the right, to the left, or does it remain unchanged?

Solution.