CfE Higher Homework
Our Dynamic Universe
Homework 5 – Newton’s Laws
1.
A lift of mass 600kg, carrying 3 people, with a mass of 70kg, 85kg
and 68kg, travels upwards at a constant speed.
Calculate the tension in the cable that pulls the lift upwards.
(2)
2.
A car of mass 600 kg is accelerated from rest to 20 m s 1 in 15
seconds.
(a) What is the size of the resultant force acting on the car? (3)
(b) How far does the car travel in these 15 seconds?
(3)
3.
(a)
(b)
(c)
4.
A rocket of mass 5·0 × 10 4 kg is launched vertically upwards
from the surface of the Earth. Its engines produce a constant
thrust of 8·0 × 10 6 N.
(i) Draw a diagram showing all the forces acting on the
rocket just after take-off.
(2)
(ii) Calculate the initial acceleration of the rocket.
(3)
As the rocket rises the thrust remains constant but the
acceleration of the rocket increases. Give three reasons for
this increase in acceleration.
(3)
Explain in terms of Newton’s laws of motion why a rocket can
travel from the Earth to the Moon and for most of the journey
not burn up any fuel.
(1)
A crate of mass 200 kg is placed on a balance, calibrated in
Newtons, in a lift.
(a) What is the reading on the balance when the lift is
stationary?
(1)
2
(b) The lift now accelerates upwards at 1·50 m s . What is the
new reading on the balance? .
(2)