Forces

Question 1

Principle of moments

Answer 1

when a lever is balanced, the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point

Question 2

Balanced forces

Answer 2

Occur when there is no resultant force on an object

Question 3

Newton’s first law

Answer 3

A body stays at rest, or if moving, it continues to make with uniform velocity, unless an unbalanced force makes it behave differently

Question 4

Unbalanced forces

Answer 4

Occur when there is a resultant force causing an acceleration

Question 5

Mass

Answer 5

Measured in KG shows amount of matter in an object

Question 6

Newtons second law

Answer 6

Force = mass x acceleration

Question 7

Friction

Answer 7

A force that always opposes motion

Question 8

Weight

Answer 8

Force of gravity on an object

Question 9

Acceleration of freefall

Answer 9

Acceleration of an object towards the surface of the Earth when the only force on it is the gravitational force

Question 10

Gravitational field strength, g

Answer 10

Gravitational force on an object of mass 1 kg close to the surface of a planet

Question 11

Equation for weight

Answer 11

Weight = force of gravity = mass X acceleration due to gravity

W = M x G

Question 12

Gravity on the moon

Answer 12

1.6 N/kg

Question 13

Deep space gravity

Answer 13

• No gravitational pulls
• G= 0
• everything is weightless

Question 14

What will happen if there is no air resistance?

Answer 14

• The speed of a falling object will increase by 10 m/s every second
• acceleration = 10 m/s2

Question 15

Hookes law

Answer 15

Extension is directly proportional to the applied load, up to a limit known as the limit of proportionality

Question 16

What happens when a body is thrown vertically upwards?

Answer 16

• Motion is opposed by the force of gravity
• velocity of the body will decrease by 10m/s in each second until it’s vertical velocity = zero

Question 17

Deceleration/retardation

Answer 17

Negative acceleration motion as opposed by force of gravity

Question 18

What does hookes law describe?

Answer 18

behaviour of metal wires and springs when they are stretched or compressed

Question 19

What is natural length in Hookes law?

Answer 19

Length of a spring, when no stretching or compressing forces are applied

Question 20

Extension in hookes law

Answer 20

The difference between the stretch length of a spring, and it’s natural length

Question 21

What do elastic materials do when the force is removed?

Answer 21

Returns to original length when stretching force is removed

Question 22

What do plastic materials do when the stretching force is removed?

Answer 22

Do you not return to original length when the stretching force is removed

Question 23

Hooks law equation

Answer 23

F = ke

Question 24

K hooks law equation

Answer 24

• Spring constant
• N/CM or N/MM
• equal to gradient of force – extension graph

Question 25

Pressure equation

Answer 25

P = F/A

Question 26

Equilibrium

Answer 26

equilibrium is a state in which opposing forces or moments are balanced

Question 27

Pressure

Answer 27

Force per unit on a surface

Question 28

Centre of gravity

Answer 28

centre of gravity is the point through which the entire weight of a body appears to act

Question 29

neutral equilibrium

Answer 29

neutral equilibrium is a state in which a slight displacement causes the object neither to move very far from its original position nor return to it le.g. a ball sitting on a bench)

Question 30

unstable equilibrium

Answer 30

unstable equilibrium is a state in which a slight displacement causes the object to move a long way from its original position (e.g. a pencil balanced on its end)

Question 31

stable equilibrium

Answer 31

stable equilibrium is a state in which a slight displacement causes the object to return to its original position (e.g. a traffic cone standing on its wide base)

Question 32

What is necessary for maximum stability?

Answer 32

- The centre of gravity should be as low as possible. - The area of the base should be as large as possible.

Question 33

What is a moment?

Answer 33

The moment about a point is the product of a force and it’s perpendicular distance from the point

Question 34

What is an incorrect direction of the moment?

Answer 34

Up or down, moments can only be clockwise or anticlockwise

Question 35

Balanced force

Answer 35

If the object of stationary it will remain stationary, if it is moving, it will carry on moving at the same speed and in the same direction

Question 36

Unbalanced forces

Answer 36

An unbalance force on an object, causes the object accelerate, according to F = MA