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CE - Physics > Forces and Motion > Flashcards

Forces and Motion Flashcards

1
Q

What is speed?

A

A measure of how far you travel in a set amount of time.

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2
Q

What is the formula for speed?

A

Speed = distance / time

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3
Q

What do distance time graphs show?

A

The distance travelled by an object over time.

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4
Q

In a distance time graph, what does the slope show?

A

The speed in which the objects moving

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5
Q

In a distance time graph, what does a flat line show?

A

The object has stopped

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6
Q

In a distance time graph, if a line is straight, what does that show?

A

It is moving at a constant speed.

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7
Q

In a distance time graph, if a line is curved, what does that show?

A

The object is accelerating or decelerating.

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8
Q

When do you use relative motion?

A

When you want to know the speed of something when you are also moving.

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9
Q

How do you calculate the relative forces of two objects moving in opposite directions?

A

Add the two speeds

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10
Q

How do you calculate the relative forces of two objects moving in similar directions?

A

Subtract one speed from the other

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11
Q

What are forces?

A

Pushes or pulls that occur when two objects interact.

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12
Q

Can you see forces?

A

No, but you can see the effects of a force.

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13
Q

What are forces measured in?

A

Newtons / N

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14
Q

Do forces usually act alone?

A

No, they act in pairs.

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15
Q

What is a newton meter?

A

Apparatus used to measure forces.

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16
Q

Do forces always act in a certain direction?

A

Yes

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17
Q

Name three non-contact forces.

A

The gravitational pull between planets, forces between magnets and forces due to static electricity.

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18
Q

What are the five things forces can make objects do?

A

Speed up / start moving - e.g. kicking a football. The push force must be bigger than the resisting forces.

Slow down / stop moving - e.g. drag or air resistance. The push force must be smaller than the resisting forces.

Change direction - e.g. hitting a ball with a bat.

Turn - e.g. turning a spanner

Change shape - e.g. stretching, compressing, bending and twisting.

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19
Q

What do balanced forces produce?

A

No change in movement.

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20
Q

What do unbalanced forces do?

A

Change the speed / direction of moving objects.

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21
Q

What is friction?

A

A force that always acts in the opposite direction to movement.

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22
Q

What are three good points about friction?

A

Allows tyres to grip the road surface.

Acts as a brake.

Lets you grip objects (e.g. a bike).

23
Q

What are two good points about friction?

A

Always wastes energy (thermal).

Limits top speed.

24
Q

What are the general four forces on a moving object?

A

Driving force - forward
Drag - backward
Weight - downward
Upward thrust - upward

25
Q

What are air and water resistance (drag)?

A

Forces that push against objects which are moving through the air or water.

26
Q

What type of force is drag?

A

A frictional force because they slow objects down.

27
Q

What does streamlined mean?

A

If an object is streamlined, then it can slip through air or water without too much resistance e.g. a sports car.

28
Q

What are the five stages a parachutist goes through?

A

Gains speed when the only force is their weight.

Still gaining speed as their air resistance increases.

Losing speed when their parachute opens as the air resistance is now greater than their weight (large surface area cuts through the air).

Steady speed when the air resistance becomes equal to the weight.

No speed when the parachutist is on the ground.

29
Q

What does resistance do?

A

Eventually makes objects fall at a steady speed by acting in the opposite direction to graivty.

30
Q

What do force diagrams show?

A

The forces acting on an object and whether they are balanced or not.

31
Q

If the arrows on a force diagram are equal, what are the forces?

A

Balanced

32
Q

If a bus was stationary when the forces balanced, what would happen?

A

It would stay stationary.

33
Q

If a bus was moving when the forces balanced, what would happen?

A

It would carry on moving at a steady speed in the same direction.

34
Q

What is a pivot / fulcrum?

A

The point around which a rotation happens e.g. the middle of a seesaw.

35
Q

How is a moment created?

A

When a force acts on something that has a pivot.

36
Q

What is the equation to calculate a moment?

A

Moment = force x perpendicular distance.

37
Q

What is a lever?

A

A rigid bar resting on a pivot, used to move a heavy load when pressure is applied to one end.

38
Q

What is a load?

A

The object you are trying to move.

39
Q

What is the effort?

A

The force applied to try to move the load.

40
Q

What does using a longer lever do?

A

It means less force is needed to produce the same turning effect.

41
Q

Why are long handled screw-drivers better to undo a screw?

A

Because the longer the screwdriver, the less force needed to undo the screw.

42
Q

What is a moment?

A

A turning force.

43
Q

What is a lubricant?

A

A substance which lowers friction between two objects.

44
Q

What happens if moments are balanced?

A

Then the lever will remain bakanced.

45
Q

What happens if moments are not balanced?

A

Then the ruler will tip to one side.

46
Q

What do we measure moments in?

A

Nm

47
Q

Which way do moments go?

A

Clockwise or anticlockwise.

48
Q

What does deform mean?

A

Change shape

49
Q

Why are springs special?

A

They always spring back into their original shape after the force is removed (they are elastic).

50
Q

What is the energy transfer of a spring?

A

The energy is transformed to elastic potential when squished, and when it springs back, it goes from elastic to kinetic.

51
Q

What does Hooke’s law say?

A

The amount a spring is stretched is directly proportional to the force applied, the relationship is linear.

52
Q

What does Hooke’s law state about the limit of extension?

A

It only applies up to a certain force.

53
Q

What is the equation for Hooke’s law?

A

F = k x e

Force = spring constant (dependant on material) x extension.

54
Q

How are forces equilibrium?

A

When a stretched or compressed spring holds a weight still, the force of the weight is the same as the force of the spring as it tries to return to its original shape.

CE - Physics (5 decks)

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