Topic 2 - Motion And Forces Flashcards

1
Q

What is a scalar quantity?

A
  • A quantity that only has a magnitude
  • A quantity that isn’t direction dependent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a vector quantity ?

A

A quantity that has both a magnitude and an associated direction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How can a vector quantity be represented ?

A

Using vector arrows

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How do vector arrows represent vectors?

A
  • The length of the arrow represents the magnitude
  • The arrow points in the associated direction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Give 3 examples of vector quantities

A
  • Velocity
  • Displacement
  • Force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Give examples of scalar quantities

A
  • temperature
  • mass
  • time
  • speed
  • distance
  • energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is velocity ?

A

The speed of an object in a specific direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Give an equation linking speed , distance and time

A

Average speed = distance / time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

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

A

The speed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

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

A

The velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do you 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

State the equation for the average acceleration of an object. Give appropriate units

A

Acceleration = change in velocity / time taken

a = m/s^2. V = m/s. t = s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Give an equation linking final velocity with initial velocity , displacement and acceleration

A

V^2 = u^2 + 2as

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

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

A

It is equal to the area under the graph

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

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

A

The acceleration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

State a typical value for the speed of sound

A

330 m/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a typical value for human walking speed?

A

1.5 m/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a typical value for human running speed?

A

3m/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is a typical value for human cycling speed?

A

6m/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Give an approximate value for the acceleration of an object in free fall under gravity near the Earth’s surface

A

10 m/s ^2

21
Q

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

A

The resultant force

22
Q

State Newton’s first law for a stationary object

A

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

23
Q

State Newton’s first law for a moving object

A

If the resultant force on a moving object is zero, the object will remain at constant velocity ( same speed in same direction. )

24
Q

State the defining equation for Newton’s second law

A

Resultant force = Mass x Acceleration

F=ma

25
Q

State Newton’s second law

A

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

26
Q

What is weight ?

A

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

27
Q

What quantities does weight depend on ?

A

Weight = mass x gravitational field strength

  • the object’s mass
  • the gravitational field strength at the given position in the field
28
Q

What is the unit used for weight?

A

Newton N

29
Q

What is the unit used for gravitational field strength ?

A

N/kg

30
Q

What piece of equipment can be used to measure an object’s weight?

A

A calibrated spring balance
A newton metre

31
Q

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

A

When the object is changing direction
E.g moving in a circle

32
Q

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

A
  • speed is a scalar quantity
  • velocity is a vector quantity which means it can only be constant if the direction is constant
  • in circular motion, the direction is continuously changing
  • velocity is constantly changing
33
Q

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

A

It is called the centripetal force and acts towards the centre of the circle

34
Q

What is inertial mass ?

A
  • a measure of how difficult it is to change a given object’s velocity
  • the ratio of force over acceleration
35
Q

State Newton’s third law

A

Whenever 2 objects interact, the forces that they exert on each other are always equal and opposite

36
Q

Equation for momentum

A

Momentum = Mass x velocity

37
Q

What unit is used for momentum ?

A

kgm / s

38
Q

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

A

The total momentum before and after are equal

39
Q

Equation linking change in momentum , force and time

A

Force x time = change in momentum

40
Q

How can you measure human reaction times?

A

Ruler drop test
- person A and B hold 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

41
Q

What is the stopping distance of a vehicle equal to?

A

Thinking distance + braking distance

42
Q

For a given braking distance, if the vehicles 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 for human reaction times

A

0.2-0.9 s

44
Q

3 factors which can affect reaction time

A

Tiredness
Drugs
Alcohol

45
Q

2 factors which may affect braking distance

A

Adverse ( wet/icy) road conditions
Poor tyre or brake 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

The braking force must also be increased

48
Q

Two consequences of a vehicle undergoing very large decelerations

A
  • kinetic energy converted to heat is very high causing brakes to overheat
  • loss of control of vehicle