Topic 2

Question 1

What must always be true when using the SUVAT equations of motion?

Answer 1

The acceleration must be unifrom - if the acceleration is changing, the equations are not valid.

Question 2

What does the gradient of a distance-time graph represent?

Answer 2

Speed

Question 3

What does the gradient of a displacement-time graph represent?

Answer 3

Velocity

Question 4

What does the gradient of a velocity-time graph represent?

Answer 4

Acceleration

Question 5

Describe the shape of a velocity-time graph for an object travelling with unifrom acceleration.

Answer 5

If accleration is constant, the gradient of the velocity-time graph will be constant and so it will form a straight line graph.

Question 6

Describe the shape of a velocity-time graph for an object travelling with non-uniform acceleration

Answer 6

If acceleration is not constant, the gradient of the velocity-time graph will change and so it will form a curve

Question 7

Compare the velocity-time graphs for a uniformly accelerating and a uniformly decelerating object.

Answer 7

For an accelerating object, the gradient will be positive

For a decelerating object, the gradient will be negative

Question 8

What is a scalar quantity

Answer 8

A scalar quantity is one that has a magnitude but not a fixed direction

Question 9

What is a vector quantity

Answer 9

A vector quantity is one that has a magnitude and a fixed direction

Question 10

Give five eamples of scalar quantities

Answer 10

Distance, Speed, Mass, Energy, Temperature

Question 11

Give five examples of vector quantities

Answer 11

Displacement, Velocity, Acceleration, Momentum, Force

Question 12

How is a vector quantity represented on a diagram?

Answer 12

As an arrow,
The direction of the arrow represents the direction of the quantity,
The length of the arrow represents the magnitude of the quantity

Question 13

What does resolving a vector involve?

Answer 13

Splitting the vector into two perpendicular components, vertical and horizontal.

Question 14

Define the horizontal component of the vector in terms of V and θ

Answer 14

x = Vcos(θ)

Question 15

Define the verticle component of the vector in terms of V and θ

Answer 15

y = Vsin(θ)

Question 16

Describe the relationship between the perpendicular components of a vector

Answer 16

The perpendicular components are independent of each other

Question 17

How should the components of a projectile be handled when carrying out calculations

Answer 17

The horizontal and vertical components are independent of each other and so should be treated separately
SUVAT should be used separately for each component

Question 18

If a projectile is moving freely under gravity, what can be said about the vertical acceleration?

Answer 18

The vertical accelaration will be the acceleration due to gravity and so will have a magnitude of 9.81m/s^2

Question 19

State Newton’s first law of motion in words

Answer 19

An object at rest will remain at rest, and an object moving with a given velocity will continue moving with that same velocity, unless acted on by an external resultant force.

Question 20

State Newton’s second law of motion in words

Answer 20

The acceleration of an object is directly proportional to the resultant force acting on it and inversely proportional to its mass.

Question 21

State the defining equation of Newton’s second law of motion.

Answer 21

F=ma

Force (N) = Mass (kg) x Acceleration (m/s^2)

Question 22

Can an object travelling with constant speed change direction, without an external force acting?

Answer 22

For an object to change direction, its velocity must change. This means there must be an acceleration. An acceleration cannot occur without an external resultant force acting.

Question 23

Describe the forces acting on an object travelling at terminal velocity

Answer 23

The forces are balanced in both the vertical and horizontal components of its motion
There is no resultant force, and therefore no acceleration

Question 24

What is meant by terminal velocity?

Answer 24

For a given set of conditions, the terminal velocity is the maximum speed of the object. An object has zero acceleration at terminal velocity

Question 25

State the equation used to calculate the weight of an object

Answer 25

W=mg | Weight = Mass x Gravitational Field Strength

Question 26

What is the unit of weight?

Answer 26

Newtons, N

Question 27

State Newton's third law of motion in words.

Answer 27

Every action has an equal and opposite reaction. This means that there is always a pair of forces acting on interacting objects, equal in magnitude, but in opposite directions

Question 28

State the equation for momentum

Answer 28

p=mv | Momentum = Mass x Velocity

Question 29

What is the unit of momentum?

Answer 29

kgm/s

Question 30

What is the consequence of the linear conservation of momentum

Answer 30

The total momentum of a system before an event is always equal to the total momentum of the system after the event.

Question 31

What is a moment?

Answer 31

A moment is the turning effect of a force

Question 32

State the equation used to calculate the moment of a force.

Answer 32

Moment of a force = Force x Distance

Question 33

What distance must be used when calculating a moment?

Answer 33

The perpendicular distance between the line of action of the force and the axis of rotation

Question 34

What is the unit of a moment?

Answer 34

Nm

Question 35

What is the principle of moments?

Answer 35

For an object to be in equilibrium, the sum of the clockwise moments about a point must be equal to the sum of the anticlockwise moments

Question 36

What is an object's centre of gravity

Answer 36

The single point through which the object's entire weight can be said to act

Question 37

What will occur if the line of action, an object's centre of gravity, lies outside its base?

Answer 37

The object's weight will produce a resultant moment and so if unsupported, the object may topple.

Question 38

State the equation used to calculate the work done by a force

Answer 38

W=FΔs | Work Done = Force x Change in Distance

Question 39

What force is used when calculating the work done by a force over a distance?

Answer 39

The component of the force that is in the direction of the object's motion

Question 40

What is the unit of work?

Answer 40

Joules, J

Question 41

What is the work done by the force, F when it moves the object a distance of x? (Triangle with angle θ, hypotinuse of F, horizontal x)

Answer 41

Work Done = Fcos(θ) x

Question 42

What form of energy do all moving objects have?

Answer 42

All moving objects have kinetic energy

Question 43

State the equation used to calculate the kinetic energy of an object

Answer 43

Ek = 1/2 mv^2 | Kinetic energy = 1/2 x Mass x Velocity^2

Question 44

What form of energy does a raised object have?

Answer 44

Gravitational Potential energy

Question 45

State the Equation used to calculate gravitational potential energy

Answer 45

``` GPE = Mass x Gravitational Field Strength x Height GPE = mgh ```

Question 46

What is the conservation of energy?

Answer 46

The law of conservation of energy states that energy cannot be created or destroyed - it can only be transferred between different forms

Question 47

What is power

Answer 47

The rate at which energy or work is done

Question 48

State two equations used to calculate power

Answer 48

P=E/t | P=W/t

Question 49

What is the unit of power?

Answer 49

Watt, W

Question 50

What is the waste energy of an electrical appliance?

Answer 50

The waste energy is the energy that is not used for the appliance's intended purpose.

Question 51

State the equation relating energy and efficiency

Answer 51

Efficiency = Useful energy output / Total energy input

Question 52

State the equation relating power and efficiency

Answer 52

Efficiency = Useful power output / Total power input

Question 53

What is the unit of efficiency?

Answer 53

Efficiency is a ratio and so doesn't have an associated unit