A force of 100 N is used to lift and 80-N weight to a height of 20 m.assuming no friction. ?

Question

a.how much work is done by the force?

b.what is the change in the potential energy of the weight?

c.what is the change in the kinetic energy of the weight?

Answer 1

W (work)= f(force) x d(distance)

= 100 x 20 = 2000 Joule

ΔPE(Potential energy) = m(mass) x g(acceleration due to gravity) x h(height) = fg(weight) x h = 80 x 20 = 1600 Joule

m = weight / g = 80 / 10 = 8 kg

a = f / m = 100/8 =12,5 m/s^2

a =12,5 = h/t^2 = 20/t^2

t = sqrt(20/12,5) =1,2649 s

v = h/t =20/1,2649 =15,8 m/s

ΔKE(Kinetic energyg) = 1/2 m v^2 = 1/2 x 8 x (15,8)^2 = 998,56 Joule