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) secure clamp stand using bosses/clamps
2) make sure ruler is perpendicular to working surface **
3) measure length of spring with 0N and record it
4) hang 100g (1N) to spring and measure and record the length (wait until stationary**)
5) repeat until we have 800g in total hanging off the spring
6) remove 100g and measure and record
7) repeat step 6 until there are no weights left
8) 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