Question

A car travels with a uniform velocity of 50m/s for 10 seconds. The brakes are then applied and car is uniformly retarded. It comes to rest in further 8s.Draw a graph of velocity against time. Use this graph to find total distance travelled.​

Answer 1

Answer:

Given, u=20m/s

t

1

=5s

t

2

=8s

Graph: (Refer to Image)

(1) Distance travelled in first 5 sec= area of ABDE= 20×s=80m

(2) Distance travelled after the brakes are applied (area of BCD)=

2

1

×8×5=20m

(3) Total distance travelled= AreaofABCDE+AreaofBCD=80+20=100m

(4) Acceleration during the first 5 sec= 0, because uniform velocity.

(5) Acceleration during the last 8 sec= v=0,u=20m/s,t=8sec

⇒v=u+at⇒0=20+a(8)

⇒a=−2.5m/s

2

(slope of the line DC)

solution