Question

The speed- time graph of a car is given in (figure) The car weights `1000kg`
(a) What is the distance travelled by the car in first two seconds?
(b) What is the braking force applied at the end of `5 seconds` to bring the car to a stop within one second?

Answer 1

(a) Here, mass of car,
`m=1000kg` distance, `s=?`
In the first two seconds, the speed- time graph is `OA`
s=area of `DeltaOAE= ("base" xx "height")/2= (OExxEA)/2` or `s=(2xx15)/2= 15m`
(b) initial speed, `u=15m//s` final speed, `v=0`
time taken, `t=1s` Barking force, `F=?`
As `F= ma= (m(v-u))/t,F= (1000(0-15))/1= -15000N`
Negative sign is for opposing force.