Question

1. A car is travelling with velocity of 72km /hr. If the car comes at rest after 5 second, when the brakes are applied. Calculate its acceleration. Also mention type of the acceleration. do with all process .

Answer 1

Answer:

u

initial

=72×

18

5

=20m/s

a

dec

=2m/s

2

(a)s=ut+

2

1

at

2

v=u+at

v=0

u−a

dec

t=0

20=2×1

t=10s

s=20×10−

2

1

×2×100

s=100m

(b)t=10s

(c)s

nth

=u+

2

a

(2n−1)

s

1st

=20−

2

2

(2×1−1)

s

1st

=19m

s

3rd

=20−

2

2

(2×3−1)

s

3rd

=15m

Answer 2

initial velocity=72km/hr- 72×5/18m/s=20m/s

final velocity=0(comes to rest)

time=5 second

using first equation of motion

v=u+at

0=20+a×5

0=20+5a

5a=20

a=20/5

a=4m/s^2