A block initially at rest on a horizontal

PHYSICS · Multi-part · CBSE · Physics · Force and Laws of Motion · Force and Laws of Motion

Problem

1.5\,\text{kg}

block initially at rest on a horizontal, frictionless table is subject to a horizontal force that varies with time as shown in the verbal graph description below. Verbal description of

F_x

vs.

t

graph (all values in SI units): • From

t=0

t=2.0\,\text{s}

F_x

is constant at

+5.0\,\text{N}

. • From

t=2.0\,\text{s}

t=4.0\,\text{s}

F_x

abruptly drops to

0\,\text{N}

and remains there. • From

t=4.0\,\text{s}

t=5.0\,\text{s}

F_x

becomes

-3.0\,\text{N}

(opposite the

+x

direction). • After

t=5.0\,\text{s}

F_x

returns to

0\,\text{N}

and stays zero. Treat the block as a point mass and ignore all other forces. (a) Determine the magnitude and direction of the block’s acceleration during each of the four time intervals defined in the description. (b) Calculate the block’s speed at

t=2.0\,\text{s}

, immediately before the force first becomes zero. (c) Determine the block’s speed and direction of motion at

t=5.0\,\text{s}

, immediately after the

-3.0\,\text{N}

interval ends. (d) Describe the subsequent motion (

t>5.0\,\text{s}

) of the block. Include in your answer whether the speed will change and why.

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