A 2.0-kg object moves in a straight line on a horizontal frictionless surface. T

Question

A 2.0-kg object moves in a straight line on a horizontal frictionless surface. The graph shows the velocity of the object as a function of time. The various equal time intervals are labeled using Roman numerals: I, II: III, IV, and V. Find net force on the object always acts along the line of motion of the object. 1. Which section(s) of the graph corresponds to a condition of zero net force? A) V only B) III only C) II and IV D) II, III, and IV E) I, III, and V 2. Which section of the graph corresponds to the application of the largest constant net force? In which section of the graph is the magnitude of the net force decreasing?

Explanation / Answer

1. C

In region II and IV the object is moving with constant velocity. So, net force is zero in these two region.

2. C

Only in region III, acceleration = a = dv/dt = constant and non-zero. We know that force F = ma. That means when acceleration a is constant, force F is also constant.

3. A

In region I acceleration = a = dv/dt decreases and becomes zero in region II. Therefore similar to acceleration net force F is decreasing in region I. In region V the force is increasing but in the opposite direction of motion giving negative acceleration and the object stops.

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