Forces

Question 1

What can force be describes as?

Answer 1

A push or a pull

Question 2

What happens when a force acts on an object?

Answer 2

It will try to move the object or change its direction or speed.
Forced can also change the shape of an object.

Question 3

What is the size of a force measured in?

Answer 3

Newton’s

Question 4

What is a force?

Answer 4

A vector

Question 5

What are the 4 forces that act on a plane?

Answer 5

Lift ⬆️
Weight/gravity⬇️
Thrust➡️
Drag/air resistance⬅️

Question 6

What does Hooke’s law state?

This is only true if…

Answer 6

Up to the limit of a proportion the extension of a helical spring is directly proportional to the load applied.

Only true if the spring is not stretched beyond a point called the limit of proportionality.
A spring stretched beyond its elastic limit will not return to its original length as it has been permanently stretched.

Question 7

What is the equation for hook’s law?

Answer 7

F = K x E
(F = force)
(K = spring constant/stiffness)
(E = extension)

Question 8

How can you write hooks law as a ratio?

Answer 8

F1 e1
— = —
F2 e2

Question 9

Four examples of compression type springs?

Answer 9

Bed mattress
Pens
Car suspension
Trampoline

Question 10

What is the turning effect of a force called?

What is the point where the object is fixed called?

Answer 10

A moment

The pivot

Question 11

What does the size of the turning effect or moment produced by a force depend on?

Answer 11

The size of the force and the distance between the force and the pivot.

Question 12

How can we work out the size of the moment?

Answer 12

Moment = force x distance from pivot (perpendicular)

M=FxD

Question 13

What are the units for a moment?

Answer 13

Nm or Ncm

Question 14

What is the principle of moments?

Answer 14

When a system is in equilibrium the sum of the moments in the clockwise direction are equal to the sum of moments in the anti-clockwise direction about a fixed point.
The principle of moments tells us what happens when a lever with several forces acting on it is balanced or in equilibrium.

Question 15

What is the clockwise moment equal to?

Answer 15

The anti-clockwise moment

Question 16

Wha happens when a load is closer or further away from the pivot?

Answer 16

The closer the load is to the pivot the smaller it’s turning effect/moment will be.
A smaller moment will not require as large a force.

Question 17

What is an objects centre of gravity?

Answer 17

The point where the total weight of the body appears to act.

If the object is a regular shape then the centre of gravity will be at the centre of the object.

Question 18

What is the centre of mass?

Answer 18

This is the point where it’s total mass appears to act.

Unless an object is very large the centre of mass and centre of gravity will be at the same point.

Question 19

How can the stability of an object be increased?

Answer 19

Lower the centre of gravity

Widen the base of the object

Question 20

What happens when a force acts on an object?

Answer 20

It exerts pressure on the object

Question 21

What does the amount of pressure depend on?

Answer 21

The size of the force and the area over which the force acts.
The smaller the are , the greater the pressure.
The greater the are, the smaller the pressure.

Question 22

Define pressure

Answer 22

Force applied per unit surface area

Eg. Newton’s per metre squared (N/m(2))

Question 23

Equation for pressure?

Answer 23

Pressure = force/area
F
P x A

Question 24

What is another word for N/m(2)

Answer 24

Pascals

Question 25

Are liquids compressible or incompressible?

Answer 25

Incompressible

Because of this they are used to transfer pressure