Chapter 4 Forces

A block of mass m is pulled at constant velocity along a rough horizontal floor by an applied force 𝑇⃗ as shown. The magnitude of the frictional force is:

• $T\ \cos\ \theta$

• $T\ \sin\ \theta$

• $Zero$

• $mg$

The “reaction” force does not cancel the “action” force because:

• The action force is greater than the reaction force

• They are on different bodies

• They are in the same direction

• The reaction force exists only after the action force is removed

You stand on a spring scale on the floor of an elevator. Of the following, the scale shows the highest reading when the elevator:

• Moves upward with increasing speed

• Moves upward with decreasing speed

• Remains stationary

• Moves downward with increasing speed

The inertia of a body tends to cause the body to:

• Speed up

• Slow down

• Resist any change in motion

• Fall towards earth

Acceleration is always in the direction:

• Of the displacement

• Of the initial velocity

• Of the final velocity

• Of the net force

A block of mass M slides down a frictionless plane inclined at an angle q with the horizontal. The normal reaction force exerted by the plane on the block is

• $Mg$

• $mg\ \sin\ \theta$

• $mg\ \cos\ \theta$

• $Zero,\ Since\ the\ plane\ is\ frictionless$

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? (decelerating)

• less than mg

• exactly mg

• greater than mg

• zero

An object of mass m is hanging by a string from the ceiling of an elevator. The elevator is moving up at constant speed. What is the tension in the string?

• Less than mg

• Exactly mg

• Greater than mg

• Cannot be determined without knowing the speed

A stone is thrown straight up. At the top of its path, the net force acting on it is

• Greater than its weight.

• Greater than zero, but less than its weight.

• Instantaneously equal to zero

• Equal to its weight.

In the absence of an external force, a moving object will

• Stop immediately.

• Slow down and eventually come to a stop.

• Go faster and faster

• Move with constant velocity