Page 78 - Physics Coursebook 2015 (A level)

Cambridge International AS Level Physics
5 The asymmetric bar shown in Figure 4.31 has a weight of 7.6 N and a centre of gravity that is 0.040 m from the
wider end, on which there is a load of 3.3 N. It is pivoted a distance of 0.060 m from its centre of gravity.
Calculate the force P that is needed at the far end of the bar in order to maintain equilibrium. [4]
0.040 m 0.060 m 0.080 m load
pivot
W = 7.6 N
Figure 4.31 For End-of-chapter Question 5.
6 a
b The engine of a car produces a torque of 200 N m on the axle of the wheel in contact with the road.
The car travels at a constant velocity towards the right (Figure 4.32). axle
ground
Figure 4.32 For End-of-chapter Question 6.
i Copy Figure 4.32 and show the direction of rotation of the wheel, and the horizontal component of the force that the road exerts on the wheel.
ii State the resultant torque on the wheel. Explain your answer.
iii Thediameterofthecarwheelis0.58m.Determinethevalueofthehorizontalcomponentof
load = 3.3 N
Explain what is meant by: i a couple
ii torque.
[1] [2]
P
the force of the road on the wheel.
[2] [2]
[1] [2]
[4] [2]
7 a
b A flagpole of mass 25 kg is held in a horizontal position by a cable
Explain what is meant by the centre of gravity of an object.
as shown in Figure 4.33. The centre of gravity of the flagpole is at
T
flagpole
cable 30°
a distance of 1.5 m from the fixed end.
i Write an equation to represent taking moments about the
left-hand end of the flagpole. Use your equation to find the
tension T in the cable.
ii Determine the vertical component of the force at the
left-hand end of the flagpole.
1.5 m weight
2.5 m
Figure 4.33 For End-of-chapter Question 7.
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