19.A car initially at rest starts with a uniform acceleration and gains a velocity of 20m/s in 4s.The displacement of the car is

solution:

a car initially starts at rest (u)=0

it is moving with uniform acceleration and the car gains velocity(v)=20m/s.

the time taken by the car is (t)=4s

we have the formula v=u+ at

20=0+4a

20=4a

a=5m/s2

we got the uniform acceleration a =5m/s2

then ,for displacement S=ut+1/2at²

=0*4+1/2*5*4*4

=1/2*5*2*4

=40m

or

displacement=(u+v)/2*t

=(0+20)/2*4

=40m

The displacement of the car is 40m