Atruck is going 30 m/s when the driver applies the brakes for 4.7 s so that the truck slows down to 20 m/s. a) what is the acceleration of the truck? b) how far does the truck go during the 4.7 s?

Answer :

(a) The acceleration of the truck is,

(b) The distance covered by the truck is, 117.8 m

Explanation :  

By the 1st equation of motion,

...........(1)

where,

v = final velocity = 20 m/s

u = initial velocity  = 30 m/s

t = time = 4.7 s

a = acceleration of the truck = ?

Now put all the given values in the above equation 1, we get:

The acceleration of the truck is,

By the 2nd equation of motion,

...........(2)

where,

s = distance covered by the truck = ?

u = initial velocity  = 30 m/s

t = time = 4.7 s

a = acceleration of the truck =

Now put all the given values in the above equation 2, we get:

By solving the term, we get:

The distance covered by the truck is, 117.8 m

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your answer is c! hope this : )