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Physics > P5 - Forces > Flashcards

P5 - Forces Flashcards

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1
Q

What is a scalar quantity?

A

A quantity that has magnitude only

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2
Q

What is a vector quantity?

A

A quantity that has magnitude AND direction

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3
Q

A vector quantity may be represented by an _______. The length of it represents the ____________. The direction of it represents the direction of the vector quantity

A

Arrow
Magnitude

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4
Q

State examples of vector quantities

A
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5
Q

State examples of scalar quantities

A
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6
Q

What is a force?

A

A force is a push or pull that acts on an object due to the interaction with another object

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7
Q

Describe the difference between contact and non-contact forces

A

Contact forces involve the physical touching of objects, whereas non-contact forces involve no contact - the objects are physically separated

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8
Q

State examples of contact forces

A
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9
Q

State examples of non-contact forces

A
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10
Q

When two objects interact, there is a force produced on ____ objects

A

Both

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11
Q

What is an interaction pair?

A

A pair of forces that are equal and opposite and act on two interacting objects (Essentially, Newton’s Third Law of Motion)

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12
Q

What is weight?

A

Weight is the force acting on an object due to gravity.

The force of gravity close to the Earth is due to the gravitational field around the Earth.

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13
Q

What does the weight of an object depend on?

A

The gravitational field strength at the point where the object is

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14
Q

State the equation that links weight, mass and gravitational field strength

A

W = mg

Where:

Weight, W, is in Newtons (N)
Mass, M, is in Kilograms (Kg)
Gravitational field strength, G, is in Newtons per Kilogram (N/Kg)

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15
Q

What is mass?

A

Mass is the amount of matter in an object.

For any given body, mass always remains constant anywhere in the universe

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16
Q

The weight of an object may be considered to act at a single point referred to as the object’s _______ __ _______

A

Centre of mass

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17
Q

What is used to measure weight?

A

A calibrated spring-balance (Newtonmeter)

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18
Q

Describe the relationship between weight and mass

A

They are directly proportional

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19
Q

What is the resultant force?

A

The net force of a point or object that has the same effect as all the original forces acting together

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20
Q

If the forces in a system are parallel, the resultant force is derived by ______ those in the same direction and ______ those in the opposite direction

A

Adding
Subtracting

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21
Q

What are free body diagrams used for?

A

Shows all the forces acting on an object.

Can help to describe the forces acting on an isolated object or system

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22
Q

When a force causes an object to move through a distance, ______ is done on the object

A

Work

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23
Q

When does a force do work on an object?

A

When the force causes a displacement of the object

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24
Q

State the equation that links work done, force and distance

A

W = Fs

where:

Work done, W, is in Joules (J)
Force , F, is in Newtons (N)
Distance, S, is in metres (M)

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25
Q

One joule of work is done when a force of one newton causes a displacement of one metre

Form a conversion equation using this information

A

1 Joule = 1 Newton-metre

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26
Q

Work done/energy transferred against the frictional forces acting on an object causes a rise in ____________ of the object

A

Temperature

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27
Q

What is distance?

A

How far an object moves

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28
Q

What is displacement?

A

Displacement is the distance and direction of an object travelled from its point of origin/initial position

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29
Q

Which four factors have an impact on the speed at which a person walks? (Think: FATD)

A

Fitness
Age
Terrain
Distance travelled

30
Q

What are the typical everyday speeds of walking, running and cycling?

A

Walking ≈ 1.5 m/s
Running ≈ 3 m/s
Cycling ≈ 6 m/s

31
Q

It is not only moving objects that have varying speed; speed of sound and wind also vary.

What is the typical value for the speed of sound in air?

A

330 m/s

32
Q

State the equation that links distance travelled, speed and time

A

S = vt

Where:

Distance, S, is in Metres (M)
Speed, V, is in Metres per second (M/S)
Time, T, is in Seconds (S)

33
Q

What is velocity?

A

Velocity is an object’s speed in a given direction

34
Q

Describe the difference between speed and velocity

A

Both measure how fast an object is moving, however speed is a scalar and velocity is a vector

35
Q

An object moving in a circle at a constant speed has a constantly changing ________ as the direction is always changing

A

Velocity

36
Q

Give an example of motion in a circle that involves constant speed but changing velocity

A

A car going around a roundabout

37
Q

If an object moves along a straight line, the distance travelled can be represented by a ________ ______

A

Distance-time graph

38
Q

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

A

The speed of an object. The steeper the graph, the faster it is going

39
Q

If an object is accelerating, how can you find the speed at any particular time?

A

Find the gradient of the tangent to the curve at that point

40
Q

State the equation that links acceleration, change in velocity and time

A

a = Δv/t

Where:

Acceleration, A, is in metres per second squared (M/S²)
Change in velocity, Δv, is in metres per second (M/S)
Time, T, is in seconds (S)

41
Q

What is acceleration?

A

The rate of change of velocity in a given time

42
Q

What is uniform acceleration?

A

Constant acceleration

43
Q

How can acceleration be calculated from a velocity-time graph?

A

By calculating a gradient

44
Q

How can the distance travelled by an object (or displacement of an object) be calculated from a velocity-time graph?

A

By calculating the area under the velocity-time graph

45
Q

If the section under a velocity-time graph is irregular, how can you find the distance instead?

A

By counting the squares and multiplying the number by the value of one square

46
Q

What does a curve on a velocity-time graph indicate about the motion of an object? How can you find the acceleration at that point?

A

A curve means the acceleration is changing (increasing/decreasing)

You can use a tangent to the curve at that point to find the acceleration

47
Q

What is the equation for uniform acceleration? (Provided on the Physics equation sheet)

A

V² - u² = 2as

Where:

Final velocity, V, is in m/s
Initial velocity, U, is in m/s
Acceleration, A, is in m/s²
Distance, S, is in m

48
Q

Near the Earth’s surface, any object falling freely under gravity has a uniform acceleration of what?

A

9.8 m/s²

49
Q

Terminal velocity through fluids + parachute + what it depends on

A
50
Q

What is Newton’s First Law of Motion?

A

If the resultant force on a stationary object is zero, the object will remain stationary.

If the resultant force on a moving object is zero, the object will continue moving at the same velocity

-> A resultant force is needed to change motion

51
Q

What is inertia?

A

The tendency of objects to continue in their state of rest or of uniform motion

52
Q

What is inertial mass?

A

A measure of how difficult it is to change the velocity of an object

53
Q

How can you calculate inertial mass?

A

Ratio of force over acceleration

M = F/A

54
Q

What is Newton’s Second Law of Motion?

A

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

55
Q

State the equation that links resultant force, mass and acceleration

A

F = ma

Where:

Force, F, is in Newtons (N)
Mass, M, is in Kilograms (Kg)
Acceleration, A, is in metres per second squared (M/s²)

56
Q

Describe an experiment to investigate the effect of varying the force on the acceleration of an object of constant mass

A
57
Q

Describe an experiment to investigate the effect of varying the mass of an object on the acceleration produced by a constant force

A
58
Q

What is Newton’s Third Law of Motion?

A

When two objects interact, the forces they exert on each other are equal and opposite

59
Q

Explain why you will not move if you lean on a wall, even though you are exerting a force

A

Due to Newton’s third law, the wall also exerts an equal and opposite force back on you. You also exert a force on the ground and the ground exerts an equal and opposite force back on you. The resultant force is zero so you remain stationary

60
Q

State the equation which links stopping distance, thinking distance and breaking distance

A

Stopping distance = thinking distance + breaking distance

61
Q

What is the thinking distance?

A

How far the car travels during the individual’s reaction time

62
Q

What is the breaking distance?

A

Distance taken to stop under the breaking force

63
Q

For a given breaking force, the greater the ______ of the vehicle, the greater the ______ distance

A

Speed
Stopping

64
Q

As a car speeds up, the thinking distance increases by a ______ factor (at the same rate as speed)

A

Linear

65
Q

As a car speeds up, the breaking distances increases. The work done to stop the car is equal to the energy in the car’s kinetic energy store. Therefore, as speed doubles, the kinetic energy increases _____-_____ , and since W=Fs and the braking force is constant, the breaking distance also increases _____-______

A

4-Fold (x^2), where X is the speed

66
Q

The greater the braking force the greater the _______. Large ________ may lead to breaks overheating and/or loss of control

A

Decelerations

67
Q

What factors increase breaking distance?

A
  • Adverse road and weather conditions
  • Poor conditions of the vehicle (faulty brakes and tyres)
  • High speeds
68
Q

What factors increase thinking distance?

A
  • Reduced reaction time through alcohol and drug use
  • High speeds
69
Q

To avoid an accident, drivers need to leave enough ______ between their car and the one in front so if they had to come to an emergency stop, it could be done safely. _____ limits also make sure accidents don’t happen often

A

Space
Speed

70
Q

What is the equation that links mass, velocity and momentum?

A

P = mv

Where:

P, in kg m/s, is the momentum
M, in kg, is the mass
V, in m/s, is the velocity

71
Q

What is the conservation of momentum?

A

In a closed system, the total momentum before an event is equal to the total momentum after the event

Physics (8 decks)

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