Question

. A lorry with mass 3500 kg is parked at the top of a steep hill with a 1–in–8 gradient when its handbrake fails. Assume that the lorry has a constant frictional resistance to motion of 500 N. The lorry rolls 40 m down the hill before crashing into a lamp post. Use the principle of conservation of energy to calculate the velocity of the lorry immediately prior to its impact with the lamp post.

Answer 1

Answer:

Given data:

Mass of the lorry,

Resistive frictional force ,

Since the steep hill is 1-in-8 gradient, slope of the hill = ;

As the lorry travels 40 m before crashing, vertical descent =

Change in potential energy ,

While rolling, work done aganist frictional force,

By principle of Conservation of Energy,

As the lorry rolls down, the potential energy is get converted to kinetic energy.(W_fri energy is lossed to do work aganist frictional force)

i.e

i.e

velocity of the lorry immediately prior to its impact with the lamp post = 9.26 m/s