A body of mass is moving with an initial speed on a straight path

PHYSICS · Subjective · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

A body of mass

m

is moving with an initial speed

u

on a straight path. A constant net force

F

acts on it in the direction of motion through a further distance

s

. (i) Derive an expression for its final speed

v

in terms of

u

F

s

, and

m

. (ii) Show that the increase in the body’s kinetic energy is equal to the work done by the force. (iii) A

1.5\,\text{kg}

cart initially moving at

2.0\,\text{m\,s}^{-1}

is pushed with a constant force of

5.0\,\text{N}

over

3.0\,\text{m}

. Using the expression obtained in part (i), calculate its final speed and the increase in kinetic energy.