A crate rests on a smooth warehouse floor

PHYSICS · Subjective · CBSE · Physics · Force and Laws of Motion · Force and Laws of Motion

Problem

A crate rests on a smooth warehouse floor. The following horizontal forces act on it at different times along the same straight line. • From

t = 0\,\text{s}

t = 4\,\text{s}

40\,\text{N}

to the east and

25\,\text{N}

to the west. • From

t = 4\,\text{s}

t = 8\,\text{s}

: an additional force of

15\,\text{N}

to the west is applied while the original forces continue unchanged. • After

t = 8\,\text{s}

: all external horizontal forces are removed. (a) For each of the three time intervals (

0

–

4\,\text{s}

4

–

8\,\text{s}

, and after

8\,\text{s}

) identify the direction of the net force acting on the crate. (b) For each interval, describe qualitatively how the velocity of the crate changes (increases, decreases, remains constant) and give a brief reason based on Newton’s First Law. (c) Sketch a possible qualitative velocity–time graph for the entire motion from

t = 0\,\text{s}

to a short time after

t = 8\,\text{s}

. Label key features clearly.

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