Question

A force of 10 N acts for 20 second on a body of mass 2 kg initially at rest. Calculate
the energy required by the body and the workdone by the applied force.​

Answer 1

Answer:

10kJ

Explanation:

F         = ma

F         = m x (v-u)/t

Ft        = mv - mu

10x20 =  2(v) - m(0)

200/2 =  v

100m/s = v

                             ΔKE    = Work Done

            1/2mv² - 1/2mu²  = W

1/2(2)(100)²  -  1/2(2)(0)²  = W

                      10000 - 0  = W

                         10000J   = W

                              10kJ   = W

Answer 2

Answer:

F = 10N

mass = 2kg

F = ma

a = F / m = 20 / 2 = 5m/s²

acceleration (a) = 5m/s²

time (t) = 20s

initial velocity (u) = 0

displacement (s) = ut + at²/2

s = 0 + 5×20² / 2

s= 5 × 20 × 20/2

s = 5 × 20 × 10  

s = 1000m

Work done = F × s  

                  = 10×1000

                   = 10000j

v = u + at

v = 0 + 5×20

v = 100m/s

Kinetic energy = 1/2mv²

                        = 1/2 × 2 × 100 × 100  

                       = 10000joules