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Physics > Topic 2 - Force And Momentum > Flashcards

Topic 2 - Force And Momentum Flashcards

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1
Q

What is a scalar quantity?

A

A quantity that only has a magnitude

A quantity that doesn’t have direction

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2
Q

What is a vector quantity?

A

A quantity that has both magnitude and direction

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3
Q

How can a vector quantity be represented?

A

Using vector arrows

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4
Q

How do vector arrows represent vectors?

A

The length of the arrow represents the magnitude

The arrow points in the associated direction

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5
Q

Give three examples of vector quantities

A

Velocity
Displacement
Force

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6
Q

Give 6 examples of scalar quantities

A 
Temperature 
Time 
Mass
Speed 
Distance
Energy
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7
Q

What is velocity?

A

The speed of an object in a specific direction

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8
Q

On a distance/time graph, what value does the gradient of the line represent?

A

The speed

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9
Q

On a displacement/time graph, what value does the gradient of the line represent?

A

The velocity

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10
Q

What must be done to calculate speed at a given time from a distance-time graph for an accelerating object?

A

Draw a tangent to the curve at the required time

Calculate the gradient of the tangent

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11
Q

State the equation for the average acceleration of an object

A

Acceleration = change in velocity/time taken

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12
Q

How can the distance travelled by an object be calculated from a velocity -time graph?

A

By the area under the graph

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13
Q

On a velocity time graph, what does the gradient of the graph represent?

A

The acceleration

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14
Q

State the typical value for the speed of sound

A

330m/s

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15
Q

What is the typical human walking speed?

A

1.5m/s

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16
Q

What Is thesypical value for human running speed?

A

3m/s

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17
Q

What is a typical value for human cycling speed?

A

6m/s

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18
Q

What is the approx. Value for gravity on earth?

A

10m/s^2

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19
Q

What is the name given to the single force that is equable to all the other forces acting on a given object?

A

The resultant force

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20
Q

State Newton’s first law for a stationary object

A

If the resultant force on a stationary object is 0, the object will remain at rest

21
Q

State Newton’s first law for a moving object

A

If the resultant force on a moving object is 0, the object will remain at constant velocity

22
Q

State the defining equation for Newton’s second law

A

Resultant force = mass x acceleration

23
Q

State Newton’s second law in words

A

An objects acceleration is directly proportional to the resultant force acting on it and inversely proportional to its mass

24
Q

What is weight?

A

The force that acts on an object due to gravity and the object’s mass

25
Q

What quantities does weight depend on?

A

The object’s mass

The gravitational field strength

26
Q

What is the unit used for weight?

A

Newton

27
Q

What is the unit used for gravitational field strength?

A

N/kg

28
Q

What piece of equit,ent can be used to measure an object’s weight?

A

A calibrated spring-balance or Newton meter

29
Q

When can an object travelling at a constant speed not have constant velocity?

A

When it is changing direction, for example moving in a circle

30
Q

Why does an object travelling at a constant speed in a circle not have a constant velocity?

A

Velocity can only be constant I’d the direction is constant
In circular motion, the direction is continuously changing
So velocity is constantly changing

31
Q

What is the resultant force that acts on an object moving in a circle called, and in which direction does it act?

A

Centripetal force

Towards the centre of the circle

32
Q

What is inertial mass?

A

A measure of how difficult it is to chang a given object’s velocity

33
Q

State Newton’s third law

A

Whenever two objects interact, the forces that they exert on each other are always equal and opposite

34
Q

State the equation for momentum

A

Mass x velocity

35
Q

What is the unit used for momentum?

A

Kim/s

Kilogram metres per second

36
Q

In a closed system, what can be said about the momentum before and after a collision?

A

They are equal

37
Q

State the equation for change in momentum

A

Force x time

38
Q

How can you measure human reaction times?

A

Using the ruler drop test

39
Q

What is the regular drop test?

A

Person A and B hold each end of a ruler with the 0cm mark at the bottom
Person A drops the ruler without telling person B
Person B catches it
The distance travelled corresponds to their reaction time

40
Q

Why is it important that the 0cm mark is at the bottom?

A

So you can see the distance directly without having to calculate it; otherwise a zero error would need to be accounted for

41
Q

What is the stopping distance of a vehicle equal to?

A

The sum of the thinking distance and braking distance

42
Q

For a given braking distance, if the vehicle’s speed is increased, what can be said about its stopping distance?

A

The stopping distance is increased with an increase in speed

43
Q

Give a typical range of values or human reaction time

A

0.2 seconds - 0.9 seconds

44
Q

Give four factors which can affect a driver’s reaction time

A

Tiredness
Drugs
Alcohol
Distractions

45
Q

Give two factors which may affect braking distance

A

Condition of the car (brakes)

Weather conditions

46
Q

Describe the energy transfers that take place when a car applies its brakes

A

Work is done by the friction force between the brakes and wheel
Kinetic energy of the wheel is converted to heat and is dissipated to the surroundings through the brake discs

47
Q

To stop a car in a given distance, if it’s velocity is increased, what must happen to the braking force applied?

A

It must also be increased

48
Q

State two consequences of a vehicle undergoing very large decelerations

A

Loss of control of the vehicle

Kinetic energy converted to heat is very high causing brakes to overheat

Physics (12 decks)

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