Question

A car acquires a velocity of 72km/h in 10seconds starting from rest . Find (a) the acceleration (b) the distance travelled in this time

Answer 1

As the body starting from rest the initial velocity becomes zero 

                                 u = 0 

As it acquires a velocity of 72km/h so final velocity will be 72km/h 

                                 v = 72 km/h 

Time taken by the car from changes its position from initial to final 

                                 t = 10 seconds 
As v - u + at 

Its acceleration will be  v - u / t 

a = v - u / t 

wait !!! the time is in seconds and speed is in km/h 

So convert speed in m/s first 

In order to convert Km/h into m/s 

we have to multiply by 5/18 

so speed in m/s will be 72 x 5/18 = 20 m/s 

Now calculate acceleration 

a = v-u/t 

a = 20 - 0 / 10 

a = 20/10 

a = 2m/s²

In order to calculate the distance apply any formula 

Like s = ut + 1/2 at ²

put all values got ,

s = 0x 10 + 1/2 x 2 x 10 x 10 

s = 0 + 100 

s = 100 m