A cyclist comes to a skidding stop in `10m`. During this process, the force on the cycle due to the road is `200N` and is directly opposite to the motion.
a. How much work does the road do on the cycle?
b. How much work does the cycle do on the road?

Explanation

(a) Work done by the road on the cycle is due to the stopping force of friction on the cycle due to the road .
This stopping force of friction is opposite to the displacement of the cycle . Therefore , angle between them , `theta = 180^(@)` . Work done by friction ,
`W_(f) = fs cos theta `
` = 200 xx 10 xx cos 180^(@)`
` = - 2000 J `
Negative work is done on the cycle which brings it to halt .
(b) According to Newton.s third law of motion , every force has an equal and opposite reaction force . So, an equal and opposite force acts on the road due to the cycle and is equal to 200 N .
But the road doesn.t undergo a dispalcement .
So , work done by the cycle on the road = 0