Question

A particle start its motion along positive x-axix at t = 0. If at t =0 ,it has x = 0, v=10m/s and a = -5m/s^2 , find distance travelled by the particle in the first three seconds ?

Answer 1

We have
v=10m/s
a= -5m/s^2
& t=3sec

Using the 2nd law of motion
s=ut+1/2at^2
s=10×3 - 1/2×(5×3^2)
=30 - 22.5
=7.5m

HOPE IT HELPS..... :D

Answer 2

t = u/a
t = 10/5
t = 2s

Velocity will be zero after 2s
Distance travelled in first 2s = ut + 0.5at^2 = 10*2 + 0.5*(-5)*4 = 10m

Displacement covered in first 3s
S = ut + 0.5at^2
S = 10*3 + 0.5*(-5)*3^2
S = 7.5

Distance covered in 3rd second = 10 - 7.5 = 2.5m

Distance covered in first 3s = 10 + 2.5 = 12.5m