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7Be > 7B Forces > Flashcards

7B Forces Flashcards

1
Q

What are the three visible effects of a force?

A

Push, pull or twist

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2
Q

Give three examples of contact forces.

A

Friction, air resistance, drag, reaction force and upthrust

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3
Q

Give three examples of non-contact forces.

A

Gravity, magnetism and electrostatic attraction

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4
Q

What is the difference between a contact and non-contact force?

A

Contact forces require objects to be touching, non-contact forces do not

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5
Q

How can forces affect an object’s speed?

A

Slow it down or speed it up

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6
Q

Why are forces measured in Newtons?

A

Isaac Newton described the laws of gravity

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7
Q

What effect will balanced forces have on a car travelling at a constant speed on 70mph?

A

Continue at same speed in same direction

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8
Q

What effect will unbalanced forces have on a tennis ball resting on a table?

A

Start to move

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9
Q

What does the length of a force arrow tell us on a force diagram?

A

The size of a force

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10
Q

How can we tell in what direction the force is acting on a force diagram?

A

The direction the arrow is pointing

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11
Q

How would we draw a pair of balanced forces acting on an object?

A

Equal sized arrows

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12
Q

Define resultant force

A

A single force which replaces all the other forces acting on an object

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13
Q

How do we calculate resultant force if the forces act in the same direction?

A

Add them together

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14
Q

How do we calculate resultant force if the forces act in the opposite direction?

A

Find the difference between them

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15
Q

How do we decide the direction of a resultant force?

A

The direction of the largest force

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16
Q

What is the resultant force acting on a stationary object?

A

0 (zero) Newtons

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17
Q

Define speed

A

How far an object travels in a given time

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18
Q

What are the standard units for speed?

A

Metres per second (m/s)

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19
Q

Which value is found at the top of the formula triangle for speed?

A

Distance (metres)

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20
Q

How do we calculate speed using a formula triangle?

A

Cover speed, we are left with distance and time separated by a division, so speed = distance / time

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21
Q

A car travels 100 metres in 10 seconds. Calculate the car’s speed in metres per second.

A

Speed = Distance / Time, Speed = 100 / 10 = 10 m/s

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22
Q

How do you convert from metres to kilometres?

A

Divide by 1000

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23
Q

How do you convert seconds to minutes?

A

Divide by 60

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24
Q

What is the rule for giving answers as decimals?

A

Give the same number of decimal places as is given in the question, or as you are told to

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25
Q

Which value is plotted along the y-axis of a D-T graph?

A

Distance

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26
Q

Which value is plotted along the x-axis of a D-T graph?

A

Time

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27
Q

What is the difference between an upward and downward sloping straight line?

A

Upward – object moves away from start Downwards – object moves back to start

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28
Q

What type of line shows us that an object is stationary?

A

Horizontal, straight line

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29
Q

What does the steepness of a sloping straight line tell us?

A

The speed

30
Q

What type of curve shows an object which is accelerating?

A

A curve which gets steeper

31
Q

How do we calculate the distance travelled in a D-T graph?

A

By finding the difference between the start and end of the line along the vertical axis

32
Q

How do we calculate the time in a D-T graph?

A

By finding the difference between the start and end of the line along the horizontal axis

33
Q

How do you determine the total distance from a D-T graph?

A

The highest point on the graph

34
Q

How do you determine the total time from a D-T graph?

A

The furthest point on the graph

35
Q

State the equation that links speed, distance and time.

A

Speed = Distance / Time

36
Q

If distance is measured in km, and time is measured in mins. What are the units for speed?

A

Km/min

37
Q

If the units for speed are miles per second. What are the units for distance and time?

A

Distance is measured in miles, time is measured in seconds

38
Q

How do speed cameras measure a car’s speed?

A

Timing how long it takes for a car to travel between two points

39
Q

Why are speed cameras used on roads and motorways?

A

To control the speed of traffic

40
Q

How are instantaneous and average speed different?

A

Instantaneous speed is the speed at a single point in time, average speed is the speed for the whole journey

41
Q

Which variable is kept the same in an experiment?

A

Control

42
Q

Which variable is measured in an experiment?

A

Dependent

43
Q

Which variable is changed in an experiment?

A

Independent

44
Q

What is the independent variable in the experiment we are carrying out today?

A

The height of the ramp

45
Q

What are the standard units for speed?

A

m/s

46
Q

What does a horizontal line mean on a Distance-Time graph?

A

The object is stationary (not moving)

47
Q

What is a non-contact force?

A

A force between two objects which are not touching

48
Q

Name two forces acting on a toy car as it travels down a ramp.

A

Gravity/weight, friction, air resistance, reaction force

49
Q

What is an independent variable?

A

Variable that is changed in an experiment

50
Q

Why must control variables be kept the same?

A

So that they do not affect the results

51
Q

What is a dependent variable?

A

Variable that is recorded during an experiment

52
Q

State two pieces of equipment you can use to measure the dependent variable.

A

Stop clock and camera phone

53
Q

How will you decide which piece of equipment to use?

A

Consider benefits and drawbacks, carry out a practice run to see which gives a more accurate reading

54
Q

Why do you need to carry out three repeats for each value of the independent variable?

A

To calculate a mean/average

55
Q

What is a prediction?

A

Statement about what you think will happen

56
Q

Define mass

A

A measure of the number of particles an object is made of

57
Q

Define weight

A

The force of gravity acting on an object

58
Q

In what direction does the force of weight act?

A

Downwards

59
Q

What happens to mass when an object is taken to a different planet?

A

Nothing, mass stays the same

60
Q

What happens to weight when an object is taken to a different planet?

A

Weight changes depending on the GFS of the planet

61
Q

State the units for gravitational field strength.

A

Newtons per kilogram, N/kg

62
Q

What is the gravitational field strength of Earth?

A

10 N/kg

63
Q

State the equation that links weight, mass and gravity.

A

Weight (N) = Mass (kg) x Gravity (N/kg)

64
Q

What is microgravity?

A

A situation where the force of gravity is very small

65
Q

Why do people often think there is zero gravity in space?

A

Objects appear to float

66
Q

How do we know that the force of gravity can be felt everywhere?

A

Planets are kept in orbit around the Sun even though they are millions of miles away

67
Q

The GFS on Earth is 10 N/kg. What is the Earth’s GFS on the ISS?

A

90% of this which is 9 N/kg

68
Q

Why do objects on the ISS appear to float?

A

They are in free fall towards the Earth

69
Q

Why doesn’t the space station crash into Earth as it falls?

A

It travels so fast that it matches the curve of the Earth, so never reaches it

70
Q

What would happen if the Earth slowed down as it travelled around the Sun?

A

It would spiral in and crash into the Sun

71
Q

Give one example of how we can experience microgravity without going into space.

A

Free fall rides in amusement parks, in a plane travelling up and down very quickly

7Be (10 decks)

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