Question

car starting from rest attains a velocity of 72km/hr in 20 sec then it travels at the speed for next 20 sec and finally it stopped in next 10 sec . find average speed. ​

Answer 1

Answer:

(A kilometre is 1000 metres) There are 3600 seconds in an hour, so Vi ... Final velocity(Vf) = 0 Vf - Vi = 0–20 = -20m/sec. S... ... A truck starts from rest with a constant acceleration

Answer 2

Answer:

answer will be 18 m/s

Explanation:

for first 20 seconds,

s=d/t

72 ×5/18m/s × 20s = D

so, distance =400 m

now for next 20 s,

s=d/t

so D= 400 m

now for last 10 s,

v= u + at

0= 20 + 10a

a=-2m/s²

now,

s= ut + ½at²

=(20) (10) +(1/2) (-2) (10)²

=200+(-100)

=100m

so, d= 100m

now average velocity= total distance /total time

=400+400+100/20+20+10

=900/50=18m/s(ANSWER)