4.14 Moments (Part 2 - Seesaws & Gears)

Question 1

What do levers do? (4)

Answer 1

• Transfer the rotational effect of a force - push one end of a lever down and the rotational around the pivot causes the other end to rise.
• Levers increase the distance from the pivot that the force is applied. This increases the size of the moment created by a given input force.
• Usually, the load is placed a short distance from the pivot. This means that the moment created by the input force exerts an output force that is much larger than the original input force.
• Levers are useful because they make lifting and moving things easier (they reduce the input force needed to provide a large output force).

Question 2

If the input and output forces are on different sides of the pivot, like in the case of scissors, they will act in __________ directions.

Answer 2

different

Question 3

Generally, is the output force or input force closer to the pivot?

Answer 3

Output force

Question 4

Describe how one gear causes another to move with it

Answer 4

• Gears are circular discs with ‘teeth’ around their edge.
• The teeth of different gears can interlock so that turning one gear causes another to turn as well. Because of how they are linked together, a gear spinning clockwise will make the next gear spin anticlockwise. This then alternates as you go from gear to gear.
• A force applied to a small gear creates a small moment. The small gear applies this force to the gear next to it. If this second gear is larger, the force is being applied further from the pivot of the larger gear, so the moment of the second gear is larger.
• A series of gears that get bigger from gear to gear will multiply the moment of the first, smallest gear.

Question 5

When two gears are connected, do the gears turn in opposite directions, or the same direction?

Answer 5

Opposite

Question 6

The _____ of the turning effect of the two gears is proportional to the ratio of the ________ of the two gears

Answer 6

ratio, radius