Question

a car moving at a speed of 15m/s stops when brakes are applied in 1.5 sec what is distance traveled by car after applying brake? assume uniform reduction in accelaration

Answer 1

I'll start with the distance covered while decelerating. Since you know that the initial speed of the car is 15.0 m/s, and that its final speed must by 10.0 m/s, you can use the known acceleration to determine the distance covered by

v

2

f

=

v

2

i

−

2

⋅

a

⋅

d

Isolate  

d

on one side of the equation and solve by plugging your values

d

=

v

2

i

−

v

2

f

2

a

d

=

(

15.0

2

−

10.0

2

)

m

2

s

−

2

2

⋅

2.0

m

s

−

2

d

=

31.3 m

 

To get the time needed to reach this speed, i.e. 10.0 m/s, you can use the following equation

v

f

=

v

i

−

a

⋅

t

, which will get you

t

=

v

i

−

v

f

a

t

=

(

15.0

−

10.0

)

m

s

2.0

m

s

2

=

2.5 s