Question

A cyclist travelling at a speed of 72 km/h comes to rest in 5 sec. What is his acceleration?

Answer 1

Answer:

Speed of both car and truck, v=72 km/h

or, v=20 m/s

Time taken to stop the car after applying the break,t

c

​

=3.0 s

Time taken to stop the truck after applying the break=t

t

​

=5.0 s

Therefore,

Retardation of the car,a

c

​

=

3

0−20

​

=−

3

20

​

m/s

2

Retardation of the truck, a

t

​

=

5

0−20

​

=−4 m/s

2

Explanation:

Answer 2

Explanation:

Here, u = 72 km/hr

= 72 × 5/18 m/s

= 20 m/s

v = 0 m/s

t = 5 sec

Therefore, a = v-u/t

= 0-20/5

= -20/5

= -4

Hence, the accleartion is -4 m/s^2