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8Ne Year 8 Science > 8B Forces > Flashcards

8B Forces Flashcards

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1
Q

State two examples of contact forces.

A

Friction, air resistance, tension, normal contact force, and Upthrust

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2
Q

State two examples of non-contact forces.

A

Magnetism, gravity, and electrostatic force.

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3
Q

What is resultant force?

A

The overall force acting on an object.

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4
Q

What do the arrows on a free body diagram show us?

A

The direction of the forces acting on an object.

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5
Q

What are balanced forces?

A

Forces equal in size, acting in opposite directions.

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6
Q

Define equilibrium.

A

The forces acting on an object are balanced.

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7
Q

Describe the effect of zero resultant force on a stationary object.

A

It remains stationary

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8
Q

Describe the effect of zero resultant force on a moving object.

A

It remains at a constant speed.

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9
Q

Define what a frictional force is.

A

A force that acts in the opposite direction to the movement of an object.

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10
Q

What is drag?

A

A frictional force where one of the surfaces is a fluid (a liquid or gas).

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11
Q

Give an example of useful frictional force.

A

Friction between tyres and breaks.

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12
Q

Give an example of unhelpful frictional force.

A

Air resistance on moving objects

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13
Q

What is streamlining?

A

Changing the shape of an object to reduce drag.

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14
Q

Describe how penguins are streamlined to swim through the water.

A

The penguin has a specific shape that means it moves through the water easily.

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15
Q

Describe how cyclists reduce drag during races.

A

They have streamlined helmets and crouch low to reduce drag.

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16
Q

Why is it useful for racing cars to be streamlined?

A

So that they can move faster.

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17
Q

Define deformation.

A

When something changes shape.

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18
Q

What is the difference between elastic and inelastic deformation?

A

Elastic- an object returns to its original shape after a force is removed, inelastic does not.

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19
Q

How does compression affect an object?

A

Squashes it.

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20
Q

How does tension affect an object?

A

Stretches it.

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21
Q

Describe how force and extension are directly proportional for springs.

A

When an increasing force is applied, the extension increases at the same rate.

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22
Q

What does spring constant tell us about an object?

A

How much force it would take a spring to stretch a certain distance.

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23
Q

Give one use for elastic materials.

A

Sports clothing

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24
Q

Give one use for brittle materials.

A

Building materials.

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25
Q

What is an elastic material?

A

When an object is deformed by returns to its original shape when the force is removed.

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26
Q

What equipment is required when investigating the elasticity of a material?

A

Clamp and retort stand, ruler, weights, spring and weight holder.

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27
Q

What happens if an object is stretched beyond its elastic limit?

A

It does not return to its original shape.

28
Q

State Hooke’s Law.

A

The force applied to a spring is directly proportional to its extension.

29
Q

What graph can be plotted when investigating the elasticity of a material?

A

Force against extension.

30
Q

How can spring extension be calculated?

A

Extended spring length – initial spring length.

31
Q

State the equation which links spring constant, force and extension.

A

Spring constant = Force ÷ Extension

32
Q

What are the units of measurement for spring constant, force and extension?

A

Spring constant (N/m), Force (N) and Extension(m)

33
Q

What is the independent variable for testing Hooke’s Law?

A

Number of masses added.

34
Q

How will you convert the length of the spring from mm into metres?

A

Divide by 1000

35
Q

How do you calculate extension?

A

Subtract the initial length from the new length when weights are added.

36
Q

What force is equal to a 100g mass?

A

1N

37
Q

What is the initial force acting on the spring?

A

0N

38
Q

How will you calculate the spring extension of each material?

A

Spring extension = force ÷ extension.

39
Q

What is a line of best fit?

A

A line that goes through most points, but is not a dot to dot.

40
Q

How do you draw a line of best fit?

A

Draw a line that goes through most of the points.

41
Q

What is the limit of proportionality?

A

The point after which the extension is not directly proportional to force.

42
Q

What is pressure?

A

A force exerted over a certain area.

43
Q

What are the units of measurement for pressure?

A

Pascals (Pa) or N/m2

44
Q

State the two factors which determine pressure exerted by an object.

A

Force/ weight and area

45
Q

Give an example of a situation where pressure is high.

A

Treading on a single nail.

46
Q

Give an example of a situation where pressure is low.

A

Lying on a bed of nails.

47
Q

Why do high heels and flat shoes exert different pressures?

A

They have a smaller area touching the floor.

48
Q

State the equation which links pressure, force and area.

A

Pressure = Force ÷ Area

49
Q

When calculating pressure, what could be used instead of force?

A

Weight

50
Q

What causes liquid and gas pressure?

A

Particles colliding with a surface.

51
Q

What does liquid or gas pressure depend on?

A

Depth and altitude.

52
Q

Why don’t we normally notice pressure on our bodies?

A

Pressure inside and outside our bodies is equal.

53
Q

State how pressure changes with depth in a liquid.

A

Pressure increases with depth in a liquid.

54
Q

Why does pressure change as you go deeper in a liquid?

A

The number of liquid particles above something increases and the force of gravity pulling these particles down also increases.

55
Q

State how pressure changes with altitude in a gas.

A

Pressure decreases with altitude.

56
Q

Why are there fewer air particles as you increase in altitude?

A

Gravity is weaker higher up.

57
Q

How do airplanes compensate for a drop in pressure outside?

A

As you increase your altitude, the pressure in the cabin decreases slightly.

58
Q

Define density.

A

The mass of a material in a particular volume, measured in kg/m3.

59
Q

What determines whether an object floats or sinks in water?

A

Its density in comparison to water.

60
Q

What is buoyancy?

A

An upward force on an object in a liquid.

61
Q

What happens when objects are placed in water?

A

Weight pulls it down and Upthrust pushes it upwards.

62
Q

What is the upward force of water acting on an object?

A

Upthrust

63
Q

How can we find the upward force of water acting on an object?

A

Find the volume of water displaced by the object

64
Q

How are large ships able to float, despite having a large mass?

A

They have a greater weight, so a greater force of Upthrust acts on them.

65
Q

Who first developed the theory of buoyancy?

A

Archimedes

8Ne Year 8 Science (10 decks)

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