State the equation for the moment of a force.
Figure 2 now shows the rod with the axle in the middle instead.
Draw an arrow on the rod that represents the force needed to keep the rod in equilibrium.
Calculate F.
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State the equation for the moment of a force.
Figure 2 now shows the rod with the axle in the middle instead.
Draw an arrow on the rod that represents the force needed to keep the rod in equilibrium.
Calculate F.
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State the principle of moments.
Figure 1 shows a force of 500 N acting at the end of a plank of wood. The force acts at right angles to the plank and at 4.1 m away from a pivot.
Figure 1
Calculate the moment of the 500 N force about the pivot.
State the unit of the moment of the force.
Use the equation moment of a force = force × distance at right angles to the direction of the force
Calculate the distance of the centre of the box from the pivot.
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Gears are used to multiply the effect of turning forces using moments.
Gear B rotates clockwise.
State the direction of gear A.
Gear A has 10 teeth.
Gear B has 50 teeth.
State how many revolutions gear A makes after 1 revolution of gear B.
Figure 2 shows two gears, B and C.
Gear B can rotate on a fixed axle.
Gear C can move up and down.
The distance between each of the teeth on gear B and on gear C is 3 mm.
Gear B moves through one complete revolution anti-clockwise.
State the direction of gear C during this motion.
After 1 complete revolution of B, determine the distance moved by gear C.
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A student investigates moments of forces.
Figure 14 shows the apparatus used.
Figure 14
The pivot is under the centre of the rod.
A magnet is fixed to one end of the rod.
A piece of modelling clay is fixed to the other end of the rod.
The system is in equilibrium.
State the relationship between the moment of the weight of the magnet and the moment of the weight of the piece of modelling clay about the pivot.
The student fixes a coil to the bench under the magnet as shown in Figure 15.
Figure 15
The coil of wire is connected to a d.c. power supply so that there is a current in the coil.
To bring the system back into equilibrium, the student hangs a 0.050 N weight on the rod, 8.4 cm away from the pivot, as shown in Figure 15.
Calculate the size of the force between the magnet and the coil.
force = .............................................................. N
Describe how the student could develop the investigation to determine if the size of the force between the magnet and the coil is directly proportional to the size of the current in the coil.
The student reverses the direction of the current in the coil.
Describe how the student can bring the system back into equilibrium without making any changes to the magnet.
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Which force will make the rod rotate about the axle?
☐ | A | P | |
☐ | B | Q | |
☐ | C | R | |
☐ | D | S |
Figure 20 shows a person trying to lift a large rock using a metal bar.
The rock weighs 1800N.
The person can only produce a downwards force of 600N.
The person cannot lift the rock.
Figure 21
[2]
............................................... turns each second
Explain how the oil improves the efficiency of the bicycle.
[3]
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☐ | A | anticlockwise, slower than gear Q | |
☐ | B | anticlockwise, faster than gear Q | |
☐ | C | clockwise, slower than gear Q | |
☐ | D | clockwise, faster than gear Q |
Which of these gives the ratio of the number of teeth on gear P to the number of teeth on gear Q?
[1]
☐ | A | 24 − 16 | |
☐ | B | 16 + 24 | |
☐ | C | 3 : 2 | |
☐ | D | 2 : 3 |
Figure 11 shows a lever used to lift a heavy load.
Figure 11
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i)
Figure 6
Gear R and gear S can rotate.
Gear R has 20 teeth.
Gear S has 60 teeth.
Gear S rotates through 2 complete revolutions.
Calculate how many complete revolutions gear R rotates by.
[2]
gear R has rotated through .............................................................. revolutions
Figure 7
Gear S can rotate on a fixed axle.
Gear T can move up and down.
Gear S has 60 teeth.
The distance between each of the teeth on gear S and on gear T is 2 mm.
Gear S moves through one complete revolution in the direction shown.
Which of these describes the motion of gear T?
[1]
☐ | A | 60 mm up | |
☐ | B | 60 mm down | |
☐ | C | 120 mm up | |
☐ | D | 120 mm down |
Figure 8
Calculate the moment of the 70 N force about point P.
State the unit.
Use the equation
moment = force × distance normal to the direction of the force
[3]
moment = ..................... unit ...............
Figure 9
The load is equal to the total weight of the sand and the wheelbarrow. The effort is the force that the worker applies to the wheelbarrow handles.
The worker applies just enough effort to lift the load.
Explain why the effort is smaller than the load.
[2]
[1]
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Figure 10 shows an arrangement of gears.
Each gear turns around a fixed axle.
Gear P is turned through one complete revolution per second.
speed(revolutions per second) | direction of rotation | |||
☐ | A | 4 | same as P | |
☐ | B | 1 | same as P | |
☐ | C | 4 | opposite to P | |
☐ | D | 1 | opposite to P |
[1]
Figure 11
The rack can move up or down when the gears turn.
The teeth on the rack are 2 mm apart.
Calculate how far the rack moves when P turns through to one complete revolution.
[2]
distance = ............................................... mm
Use the principle of moments to calculate the mass of the toy elephant.
The metal tube is filled with oil.
The piston Y is pushed down with a force K.
This produces a force L on piston Z.
The pressure exerted on the oil by piston Y is the same as the pressure exerted by the oil on piston Z.
Explain the difference between the size of force K and the size of force L.
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The forces shown have the same magnitude but act in different directions.
Figure 1
In which of these could the forces acting on a seesaw be in equilibrium?
☐ | A | ||
☐ | B | ||
☐ | C | ||
☐ | D |
Figure 2 shows an open door.
Figure 2
Explain why it is easier to close the door by pushing at point P rather than pushing at point Q.
Figure 3 is a diagram of the forces acting on a swing.
The swing is not moving.
Figure 3
The seat of the swing, AB, is 0.80 m long. A person of weight 450 N sits on the seat. The person’s weight acts at a distance of 0.50 m from A as shown in Figure 3.
Ignore the weight of the seat.
The upward forces exerted by the ropes on the seat are F1 and F2.
Calculate the force F2 by taking moments about A.
force F2 = ...............................N
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