Question

The 10kg block is subjected to the force shown in Figure determine its velocity when t = 2s if v = 0 when t = 0.

Answer 1

f=ma

f=20t

f=20×2=40N

since t=2s

f=ma

40=10×a

a=4m/s^

v=u+at

u=0.....(given)

v=at

v=4×2

v=8m/s is the answer

Answer 2

Solution:

let, the mass of the block be M

v1 be the velocity of the block when t = 0

v2 be the velocity of the  block when t = 2s

a be the acceleration of the block.

F be the force on the block

given, M = 10kg

           v1 =0= 0

           F = (20t)N

force, F  when t= 2s

          F = 20*2= 40 N

when a force F is applied to the block will move with a acceleration.

so, acceleration, a = change in velocity of the block

     a = v2 - v1

     a = v2    since, v1 = 0

we know, force = mass* acceleration

F = Ma

F =Mv2    since, a=v2

v2= F/M

v2 = 40/10

 v2 =4 m/s

therefore, the velocity of the block when t = 2s is 4 m/s.