Question

Calculate the work done on a cyclist if a braking force of 40 N slows the cyclist from 20 ms-1to 15 ms-1 in 2s.A. 1400 JB. 1500 JC. 1600 J

Answer 1

Given,

The braking force, F=40 N

The initial velocity of the cyclist, u=20 m/s

The final velocity of the cyclist, v=15 m/s

The time duration, t=2 s.

From the equation of motion,

`d=(1)/(2)(v+u)t`

Where d is the distance traveled by the cyclist after applying the brake and before acquiring the final velocity.

On substituting the known values,

`\begin{gathered} d=(1)/(2)*(15+20)*2 \\ =35\text{ m} \end{gathered}`

The work done on the cyclist is given by,

`W=F* d`

On substituting the known values,

`\begin{gathered} W=40*35 \\ =1400\text{ J} \end{gathered}`

Therefore the work done on the cyclist is 1400 J.

Thus, the correct answer is option A.