Unit 2A Multiple Choice Review

Which of the following system of forces provides the block the smallest net force?

• 
• 
• 
• 

Each of the diagrams below represents two weights connected by a massless string which passes over a massless, frictionless pulley. In which diagram will the magnitude of the acceleration be the largest?

• A

• B

• C

• D

In the system shown above, the acceleration of the 4 kg block is

• 3.27 m/s/s

• -3.27 m/s/s

• 1.40 m/s/s

• -1.40 m/s/s

An elevator is being lifted up an elevator shaft at a constant speed by a steel cable as shown in the figure above. All frictional effects are negligible.  In this situation, forces on the elevator are such that:

• the upward force by the cable is greater than the downward force of gravity.

• the upward force by the cable is equal to the downward force of gravity.

• the upward force by the cable is smaller than the downward force of gravity.

• the upward force by the cable is greater than the sum of the downward force of gravity and a downward force due to the air.

• None of the above. (The elevator goes up because the cable is being shortened, not because an upward force is exerted on the elevator by the cable).

A woman exerts a constant horizontal force on a large box. As a result, the box moves across a horizontal floor at a constant speed “vo”.  The constant horizontal force applied by the woman:

• has the same magnitude as the weight of the box.

• is greater than the weight of the box.

• has the same magnitude as the total force which resists the motion of the box.

• is greater than the total force which resists the motion of the box.

• is greater than either the weight of the box or the total force which resists its motion.

A woman exerts a constant horizontal force on a large box. As a result, the box moves across a horizontal floor at a constant speed “vo”.  If the woman suddenly stops applying a horizontal force to the box, then the box will:

• immediately come to a stop.

• continue moving at a constant speed for a while and then slow to a stop.

• immediately start slowing to a stop.

• continue at a constant speed.

• increase its speed for a while and then start slowing to a stop.

A woman exerts a constant horizontal force on a large box. As a result, the box moves across a horizontal floor at a constant speed “vo”. If the woman doubles the constant horizontal force that she exerts on the box to push it on the same horizontal floor, the box then moves:

• with a constant speed that is double the speed “vo” in the previous question.

• with a constant speed that is greater than the speed “vo” in the previous question, but not necessarily twice as great.

• for a while with a speed that is constant and greater than the speed “vo” in the previous question, then with a speed that increases thereafter.

• for a while with an increasing speed, then with a constant speed thereafter.

• with a continuously increasing speed.

The diagram below shows a 5 kg particle with a variety of forces acting upon it; the magnitudes of the forces are labeled. The acceleration of this particle would be:

• +2.0 m/s/s

• -2.0 m/s/s

• -0.5 m/s/s

• +0.5 m/s/s

• 0

An object is moving rightward and increasing its speed.  Which of the following could be the force diagram for this object?

• A

• B

• C

An elevator of mass M is pulled upwards at constantly decreasing velocity by a massless cable.  What is the tension in the cable?

• less than zero

• between zero and Mg

• equal to Mg

• greater than Mg

• zero