Turning Effects Of Forces

A uniform beam is pivoted at its midpoint. An object is placed on the beam as shown.

Which force will re-balance the system?
1. 20 N acting downwards, 40 cm to the right of the midpoint
2. 20 N acting upwards, 40 cm to the right of the midpoint
3. 50 N acting downwards, 10 cm to the left of the midpoint
4. 50 N acting upwards, 10 cm to the left of the midpoint
A girl uses paper-clips to balance a toy bird on her finger as shown.

What is the effect of the paper-clips?
1. They help to raise the centre of gravity above the finger.
2. They help to raise the centre of gravity to her finger.
3. They help to lower the centre of gravity below ther finger.
4. They do not affect the centre of gravity but increase the weight.
A load is to be moved using a wheelbarrow. The total mass of the load and wheelbarrow is 60 kg.
The gravitational field strength is 10 N/kg.

What is the size of force F needed just to lift the loaded wheelbarrow?
1. 350 N
2. 430 N
3. 600 N
4. 840 N
Forces are applied to a beam pivoted at its centre.

Which example demonstrates the Principle of Moments?
1. A
2. B
3. C
4. D
The diagram shows four shapes, cut from the same piece of card.

Which shape has its centre of gravity nearest to the base line?
1. A
2. B
3. C
4. D
The centre of gravity of the piece of card in the diagram is at B. A disc is then attached as shown.

Which letter shows a possible position of the centre of gravity of the card-disc combination?
1. A
2. B
3. C
4. D
The diagram shows a uniform beam pivoted at its centre. Forces of 3 N and 4 N act in the direction shown.

What is the size and position of the upward force that will prevent the beam from turning?
1. size: 1 N ; position: X
2. size: 1 N ; position: Y
3. size: 7N ; position: X
4. size: 7N ; position: Y
If a nut and bolt are difficult to undo, it may be easier to turn the nut by using a longer spanner.
This is because the longer spanner gives ............................
1. a larger turning moment
2. a smaller turning moment
3. less friction
4. more friction
A door requires a minimum moment of 32.5 Nm in order to open it.

What is the minimum distance of the handle from the hinges, if the door is to be pulled open with force at the handle
of 50 N?
1. 0.33 m
2. 0.65 m
3. 0.77 m
4. 1.54 m
A metal bar, PQ, has a weight of 5 N and is pivoted at P.
It is prevented from turning by a newton meter acting at Q.

What is the reading on the newton meter?
1. 2.5 N
2. 5 N
3. 8 N
4. 10 N
The diagram shows a gauge which measures the amount of liquid in the tank.

Where should the pivot be placed so that the pointer moves the greatest distance as tank is emptied?
1. A
2. B
3. C
4. D
The diagram shows a uniform metre rule pivoted off-centre but kept in equilibrium by a suspended mass of 240 g.

If the mass of the rule acts at the 50 cm mark, what is the mass rule?
1. 12 g
2. 24 g
3. 45 g
4. 120 g
A uniform beam is balanced its centre point. An object weighing 60 N is placed 30 cm from the beam's midpoint on the left. In order to balance, a force must be applied.

Which of the following will balanced the beam?
1. 50 N downwards, 40 cm from the centre on the right.
2. 50 N upwards, 40 cm from the centre on the right.
3. 90 N downwards, 10 cm from the centre on the right.
4. 30 N downwards, 60 cm from the centre on the right.
A uniform beam is pivoted at its centre b as shown. The directions of the acting forces, 3 N and 4 N, are represented in the diagram below.

What would be the ideal magnitude and position of the force that will prevent the beam from turning?
1. magnitude: 7 N; position: c
2. magnitude: 7 N; position: b
3. magnitude: 7 N; position: a
4. magnitude: 1 N; position: c
A nut can be loosen more easily with .........................
1. a heavy spanner because a larger force can be produced.
2. a shorter spanner because a larger force can be produced.
3. a shorter spanner because a larger turning effect can be produced.
4. a longer spanner because a larger turning effect can be produced.
The diagram shows a wheelbarrow and its load, which have a total weight of 150 N. This is supported by a vertical force F at the ends of the handles.
What is the value of F?
1. 75 N
2. 150 N
3. 225 N
4. 300 N
The diagrams show the cross-sections of different glasses.

Which one is the least stable when filled with a liquid?
A hole is drilled in a square tile. The diagram shows the tile hanging freely on a nail.

Where is the centre of gravity of the tile?
1. A
2. B
3. C
4. D
A uniform bar is pivoted at its center as shown.

What force F is needed to balance the bar?
1. 3 N
2. 4 N
3. 6 N
4. 8 N
What is most likely to make an object very stable?
1. Position of centre of mass: high ; Size of base: small
2. Position of centre of mass: high ; Size of base: large
3. Position of centre of mass: low ; Size of base: small
4. Position of centre of mass: low ; Size of base: large

Turning Effects Of Forces

Multiple Choice Questions