Question

A car travels with a uniform velocity of 20 ms–1 for 5 s. The brakes are then applied and the car is uniformly retarded. It comes to rest in further 8 s. Draw a graph of velocity against time. Use this graph to find :
(i) the distance travelled in first 5 s.
(ii) the distance travelled after the brakes are applied.
(iii) total distance travelled, and
(iv) acceleration during the first 5 s and last 8 s.

Answer 1

Answer:

the only thing I have a great day and I have a few UI design for a great day of my life with a great day ahead of you who have been working on the new Sprint network and

Answer 2

100m ; 80m ; 180m ; zero and -2.5 m/s2

Explanation:

Initial velocity, u = 20 ms–1

Time taken, t = 5s

acceleration = 0 as car is retarded.

 

(i) Distance travelled in first 5 seconds:

s = ut + 1/2 at^2

= 20 * 5 + 1/2 * 0 * 0.5^2

= 100 m

(ii) Distance travelled after the brakes are applied:

u = 20 m/sec

v = 0 m/sec

t = 8 seconds

v = u + at

a = (v- u) / at = -20 / 8 = -2.5 m/s2

s = (v^2 - u^2) / 2a

=  (-20)^2 / -5

 = 400 / 5

 = 80 m

(iii) Total distance travelled by the car = 100 + 80 = 180m.

(iv) Acceleration for the first 5 seconds = 0

(v) Acceleration for the last 8 seconds = -2.5 m/s2