# A car is travelling at 72 kilometer per hour . When brakes are applied it experiences a uniform acceleration of 2 meter per second.How long does it take the car to stop? How far does it travel from the instant brakes are applied

2
by sethjoanna012

2015-04-20T20:20:24+05:30
72 kmph =72(5/18)=20
v=u+at
0=20=(-2)t
0=20-2t
2t=20
t=20/2=10sec
s=ut+0.5at^2
s=20(10)+0.5(-2)(10^2)
s=200-100
s=100m
The car travels 100m before it stops and it takes 10sec to stop

10)
2015-04-22T14:25:16+05:30

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U = 72 kmph = 72 * 5/18 = 20 m/s
a = - 2 m /s²
v = 0

the equation of motion in single dimension is :
v = u + a t
0 = 20 - 2 * t
t = 10 seconds.

s = u t + 1/2 a t²
= 20 * 10 - 1/2 * 2 * 10²
= 100 meters.

OR,    v² = u²  + 2 a s
s = ( 0²  - 20² ) / -2 * 2
= 100 meters