An object with a mass of 32 kg has an initial energy of 500 J. At the end of the experiment, the velocity of the object is recor
ded as 5.1 m/s. If the object travelled 50 m to get to this point, what was the average force of friction on object during the trip? Assume no potential energy. Show all work
Explanation: the concept of conservation of the mechanical nerve initial Em₀ = 500 J The energy is totally kinetic Em₀ = K = ½ m v₀² v₀ = v₀ = √ (2 500/32) v₀ = 5.59 m / s v² = v₀² - 2 a x the negative sign is because its stopping a = a = (5.59² - 5.1²) / 2 50 a = 0.0524 m / s² Newton's second law F = ma F = 32 0.0524 F = 1.68 N
Assuming no air resistance, once released by the pitcher, the speed must keep constant through all the trajectory, so the kinetic energy of the ball can be expressed as follows:
B)
Neglecting air resistance, total mechanical energy must be the same at any point, so, if we choose the ground level as the zero reference level for the gravitational potential energy, and assuming that the ball attains this kinetic energy just before striking ground, this value must be equal to the gravitational potential energy just before be dropped, so we can write the following equality: