12.6 CHAPTER 12. FORCE,MOMENTUM AND IMPULSE
While the combination of the two trolleys is moving at 3 m·s−^1 , the spring is released
and when it has expanded completely, the 2 kgtrolley is then moving tothe right at
4,7 m·s−^1 as shown below.
A
1 kg
B
2 kg
4,7 m·s−^1
After
(a) State, in words, the principle of conservation of linear momentum.
(b) Calculate the magnitude and direction of the velocity of the 1 kg trolley imme-
diately after the spring has expanded completely.
- [IEB 2002/11 HG1]A ball bounces back from the ground. Which of the following
statements is true of thisevent?
(a) The magnitude of the change in momentumof the ball is equal to themagnitude
of the change in momentum of the Earth.
(b) The magnitude of the impulse experienced by the ball is greater thanthe magni-
tude of the impulse experienced by the Earth.
(c) The speed of the ball before the collision will always be equal to the speed of
the ball after the collision.
(d) Only the ball experiences a change in momentum during this event.
- [SC 2002/11 SG] Aboy is standing in a small stationary boat. He throws his school-
bag, mass 2 kg, horizontally towards the jetty with a velocity of 5 m·s−^1. The com-
bined mass of the boy and the boatis 50 kg.
(a) Calculate the magnitude of the horizontal momentum of the bag immediately
after the boy has thrownit.
(b) Calculate the velocity (magnitude and direction) of the boat-and-boy immedi-
ately after the bag is thrown.
Torque and levers
- State whether each of the following statements are true or false. If the statement is
false, rewrite the statement correcting it.
(a) The torque tells us what the turning effect ofa force is.
(b) To increase the mechanical advantage of a spanner you need to move the effort
closer to the load.
(c) A class 2 lever has the effort between the fulcrum and the load.
(d) An object will be inequilibrium if the clockwise moment and the anticlockwise
moments are equal.
(e) Mechanical advantage is a measure of the difference between the load and the
effort.
(f) The force times the perpendicular distance iscalled the mechanical advantage.
- Study the diagram below and determine whether the seesaw is balanced. Show all
your calculations.
1,2 m 2 m
5 kg 3 kg
