P2.3: Forces In Action

Question 1

What could happen when you apply a force to an object?

Answer 1

Compress
Stretch
Bend

Question 2

What does it mean when an objects shape is being changed?

Answer 2

Deformed

Question 3

What are the two different types of deformation?

Answer 3

Elastic
Inelastic

Question 4

What is elastic deformation?

Answer 4

If an object returns back to its original shape after the forces are removed

Question 5

What is inelastic deformation?

Answer 5

If an object doesn’t return back to its original shape after the forces are removed - stays deformed
Plastic deformation sometimes called.

Question 6

What is extension?

Answer 6

The increase in length of a spring when stretched

Question 7

What happens to the force at the bottom of a spring as you add more mass?

Answer 7

Extension increases proportionally

Force is directly proportional to extension

Question 8

What is spring constant?

Answer 8

How much an elastically deformed object stretches for a given force
It usually depends on the type of material being stretched
Stiffer material - larger Spring constant

Question 9

What does hooke’s law help us determine?

Answer 9

The relationship between the extension of a spring and force

Question 10

What is hookes law?

Answer 10

Force exerted by a spring (N) = extension (m) x spring constant (N/m)

Question 11

What happens to an object when you reach the limit of proportionality of its extension?

Answer 11

Most still deform a little bit
If you increase the deforming force, you reach a point where its elasticity runs out and it starts to deform plastically - the object won’t spring back to its original shape after stretching force is removed
Permanently deformed

Question 12

What is the elastic limit?

Answer 12

Maximum force that can be applied to a material before it is permanently deformed
Hookes law is no longer obeyed

Question 13

What is the relationship between force and extension of plastic materials?

Answer 13

Non linear
Graphs are curved
Elastic limit so low
Never see any actual elastic deformation

Question 14

What is done to deform an object?

Answer 14

Work is done

Question 15

What happens to energy in an elastic deformation?

Answer 15

Energy is transferred to the object’s elastic potential energy store

Question 16

What is the equation for energy stored in an objects elastic potential energy store?

Answer 16

Energy transferred in stretching = 0.5 x spring constant x (extension)2

Question 17

What could happen when a force acts upon an object with a pivot?

Answer 17

Can cause the object to rotate around the pivot

Question 18

What is a moment?

Answer 18

The turning effect of a force - the ability of an object to rotate or turn about a fixed point

Question 19

How can we calculate the size of a moment?

Answer 19

Moment of a force = force (N) x distance (m)

Question 20

If we took the example of a nut and a spanner, what would happen if we used a longer spanner, while still applying a regular force on a normal one?

Answer 20

Same force exerts a larger moment because distance from the pivot is greater

Question 21

Which ways can force cause an object to pivot?

Answer 21

Clockwise
Anticlockwise

Question 22

What do levers do?

Answer 22

Transfer the turning effect of a force

Question 23

How can levers act as force multipliers?

Answer 23

Increase the distance from the pivot that the force is applied, less input force is needed to get the same moment.
They reduce the force needed to get the same moment

Question 24

How do gears work?

Answer 24

Teeth interlock, turning each other together
A gear spinning clockwise will make the other gear spin anticlockwise
This then alternates as you go gear to gear

Question 25

What happens when particles in a fluid bump the sides of a container?

Answer 25

Pressure in a fluid is transmitted equally in all directions and it causes a force at right angles to any surface

Question 26

How do hydraulics work?

Answer 26

The system has two pistons, one with a smaller cross-sectional area than the other. Pressure is transmitted equally through a liquid - so the pressure at both pistons is the same. But the second piston has a larger area, so there is a larger force

Question 27

How can you calculate pressure from the force and area of the surface that the force is being exerted on?

Answer 27

Pressure (Pa) = force normal to a surface (N) / area of that surface (m2)