Forces and Elasticity and Moments, Levers and Gears

Question 1

How do forces change the shape of a stationary object?

Answer 1

• by stretching, bending or compressing it

Question 2

What is elastic deformation?

Answer 2

• object goes back to its original shape after it has been deformed

Question 3

What is inelastic deformation?

Answer 3

• material does not return to original shape when force is removed
• pernament change of shape

Question 4

Why do you need 2 forces to bend, compress or stretch an object?

Answer 4

• if one force is applied, it would only move

Question 5

describe the forces in stretching an object

Answer 5

• two forces pulling away from each other

Question 6

describe the forces in compressing an object

Answer 6

• pushing towards each other

Question 7

describe the forces in bending an object

Answer 7

• one force acting clockwise
• other acting anticlockwise

Question 8

What is the rule between the extension of an object and the force applied?

Answer 8

• extension of an elastic object is directly proportional to the force applied
• as long as limit of proportionality/ elastic limit is not exceeded

Hooke’s law

Question 9

What is the equation between force, spring constant and extension?

Answer 9

Force = Spring Constant x Extension
F = k x e

k = N/m
e = m

F = N

Question 10

Explain the method for investigating the relationship between load and extension for a spring

Answer 10

1) set up stand with ruler, spring, weights
2) measure length of spring with 0N and record it
3) hang 100g (1N) to spring and measure and record the length
4) repeat until we have 800g in total hanging off the spring
5) remove 100g and measure and record
6) repeat step 5 until there are no weights left
7) subtract the original length with the stretched length to get extension

Question 11

how do you calculate the spring constant?

Answer 11

• spring constant = 1/gradient

Question 12

What is the moment of a force?

Answer 12

• the turning effect of a force

Question 13

How do you calculate a moment?

Answer 13

m = F x d
d = perpendicular distance from the pivot to the line of action of the force

moment = Nm
force = newtons
distance = m

Question 14

describe the forces of a balanced object about a pivot

Answer 14

• total clockwise moment = total anticlockwise moment

Question 15

How are levers used to lift objects?

Answer 15

• clockwise force from effort = clockwise moment
• moment > force of load
• rotates/ lifts load
• lever acts as a force multiplier

Question 16

How do cogs transmit rotation force and motion from one part of a machine to another?

Answer 16

• each gear in series reverses direction of motion
• larger circumference = slower but more force
• small circumference = faster but less force