Question

A constant force of 5N is being applied continuously on a body of mass 10 kg for 4 seconds. The body moves 800cm along a straight line. What is the velocity of the body when the force is applied initially?

Answer 1

Given f = 5N, m = 10 kg, t = 4sec, s = 8m, f = ma i.e a = 2

We know that s = ut + 1/2at^2

                         8 =  u * 4 + 1/2 * 2 * 4 * 4 

                        8 = 4u + 16

                        1/2 = 4u

                      u  = 1/8 m/s



Hope this helps!

Answer 2

Given,
F=5N
m=10kg
We know,
F=ma
=>5=10×a
=>5/10=a
=>1/2=a
=>a=1/2

Given,
t=4s
Distance(S)=8m

By second equation,
S=ut+1/2a×t×t
=>8m=4u+1/2×1/2×4×4
=>8=4u+1/4×4×4
=>8=4u+4
=>8=4(u+1)
=>8/4=u+1
=>2=u+1
=>2-1=u
=>u=1m/s
By first equation,
v=u+at
=1+1/2×4
=1+2
=3m/s
《Velocity=3m/s》