Question

Q4. What will be the work done by frictional force if a rolling ball of 500 g
mass slows down from 6 m/s to 2 m/s in 10 seconds.
​

Answer 1

Explanation:

Given :

Mass of ball = 500g = 0.5kg

Initial velocity = 6m/s

Final velocity = 2m/s

Time interval = 10s

To Find :

Work done by frictional force.

Solution :

As per work energy theorem, work done by force is equal to the change in kinetic energy..

Mathematically, W = k' - k

k' denotes final kinetic energy

k denotes initial kinetic energy

Kinetic energy of body of mass m moving at a velocity of v is given by, k = 1/2 mv²

➙ W = k' - k

➙ W = 1/2 m [v² - u²]

v denotes final velocity

u denotes initial velocity

By substituting the given values;

➙ W = 0.5/2 [(2)² - (6)²]

➙ W = 0.25 [4 - 36]

➙ W = 0.25 × (-32)

➙ W = -8 J

Here negative sign shows that frictional force opposes motion in forward direction.