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Science 2021. > Forces. > Flashcards

Forces. Flashcards

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1
Q

What is a force?

A

A force is a push or a pull.

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2
Q

What can forces make a body do?

A 
Move.
Change shape.
Alter the direction in which it is moving.
Make it go faster.
Make it go slower.
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3
Q

What are forces measured with and what is the unit for force?

A

Forces are measured with a force meter and the unit is Newton (N).

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4
Q

Define resultant force.

A

A resultant force is a single force that has the same effect as all the forces acting on an object.

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5
Q

Define contact force.

A

Contact forces are forces that act between two objects that are physically touching each other.

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6
Q

Examples of contact force.

A

Mechanical forces and friction.

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7
Q

Define non-contact force.

A

A non-contact force is a force that acts on an object without coming physically in contact with it.

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8
Q

Examples of non-contact force.

A

Gravitational, electrostatic, and magnetic.

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9
Q

Define mass.

A

Mass (kg) is the amount of matter in an object.

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10
Q

Define weight.

A

Weight (N) is the pull of gravity on an object

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11
Q

When forces are balanced, what is the resultant force?

A

When forces are balanced, the resultant force is zero. The body is in equilibrium and does not move.

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12
Q

When forces are unbalanced?

A

When forces are unbalanced a body moves in the direction of the biggest force.

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13
Q

Forces in the same direction are _____ to give a resultant force.
Forces in the opposite direction are _____ to give the resultant force.
Forces in parallel are ______ together to give the resultant force.

A

Forces in the same direction are added to give a resultant force.
Forces in the opposite direction are subtracted to give the resultant force.
Forces in parallel are added together to give the resultant force.

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14
Q

Define friction.

A

Friction is a contact force that opposes movement.

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15
Q

Factors that affect friction are?

A

Type of surface in contact.
The surface area in contact.
The weight of the object.

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16
Q

Why should only one factor be investigated at a time in experiments?

A

Only one factor should be investigated at a time to ensure that the results are not biased.

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17
Q

Name the two types of friction.

A

Static and dynamic friction.

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18
Q

Define static friction.

A

Static friction is the force that needs to be surpassed for an object to start moving.

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19
Q

Define dynamic friction or kinetic friction.

A

Whilst an object is in motion, it will experience an opposing force. This is called dynamic friction or kinetic friction.

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20
Q

Name 5 ways to reduce friction.

A

Rollers, ball bearing, wheels, greasing, and oiling.

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21
Q

Rollers, ball bearings, and wheels are round objects put between the ______ __ _____.

A

Rollers, ball bearings, and wheels are round objects put between the surface in contact.

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22
Q

Ball bearings are present in all moving parts of 3 objects. Name them.

A

Cars, bicycles, and complicated machines.

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23
Q

These bearings are ____ to even further reduce the force of friction.

A

Greased.

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24
Q

Frictional force can be increased and this can be useful in 4 ways. Name them.

A

Brake pads, tyre treads, rough road surfaces, and soles of shoes.

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25
Q

What happens when the brakes are applied.

A

Brake pads apply pressure to brake discs when brakes are applied causing the car to stop. The brake discs become hot.

26
Q

Why are tyre treads rough?

A

Tyre treads are rough to increase friction between the tyre and the road surface to help prevent the car from skidding.

27
Q

Explain why rubber tyres have grooves?

A

Rubber tyres have grooves so that when the car is travelling slowly during the wet season, the grooves in the rubber tyres squeeze the water out, preventing skidding.

28
Q

What happens if the car is travelling fast during the wet season?

A

Water gets trapped in the grooves of the rubber tyres resulting in less friction and the car becomes difficult to control and skids.

29
Q

Why should tyres be replaced once the grooves disappear?

A

Smooth tyres result in less friction. The driver is more likely to lose control and the car is more likely to skid.

30
Q

Rough road surfaces, such as ____, are used at ___ and ___ ____, so that car tyres can ____ and stop more _____.

A

Rough road surfaces, such as pavers, are used at robots and traffic circles, so that car tyres can grip and stop more easily.

31
Q

What happens when the road surface gets wet?

A

When the road surface gets wet the water fills the projections in the road making it smoother.

32
Q

Why should road surfaces not be smooth?

A

This reduces friction and cars take a long time to stop as the tyres cannot grip the road surface.

33
Q

Forces can also make a body? Give 2 examples of this.

A

Forces can also make a body turn round a fixed pivot. E.g. see-saw and opening/closing a door.

34
Q

How do you calculate moment of force?

A

moment of force (Nm) = force (N) x perpendicular distance from the pivot (m).

35
Q

Define moment.

A

Turning effect of force.

36
Q

How can the moment be increased? Name 2 examples of this.

A

The moment can be increased by applying the force as far away from the pivot as possible. For example:

  • Door handles are further away from the hinges (pivots)
  • When removing a wheel nut it is easier to use a spanner with a long handle than one with a short handle.
37
Q

When removing a wheel nut it is easier to use a spanner with a long handle than one with a short handle. Explain why?

A

Because there is a longer lever arm. A longer lever arm will give a greater torque (a force that causes rotation) than a shorter one with the same applied force.

38
Q

Moments can be 2 things. Name them?

A

Clockwise and anti-clockwise.

39
Q

Moment on LHS > Moment on RHS =
Moment on LHS < Moment on RHS =
Moment on LHS = Moment on RHS =

A

Moment on LHS > Moment on RHS = anti-clockwise moment.
Moment on LHS < Moment on RHS = clockwise moment.
Moment on LHS = Moment on RHS = equilibrium.

40
Q

What does the principle of moments state?

A

The principle of moments states that for an object to be balanced the clockwise moment must be equal to the anti-clockwise moment.

41
Q

What is the resultant force for an object to be in equilibrium?

A

Zero.

42
Q

What is a machine?

A

A machine is an energy converter that reduces human effort by having several parts, each with a specific function, and together performing a particular task.

43
Q

Machine make our lives easier by?

A

Reducing the amount of energy, time, and power we need to get work done by magnifying the effort put in.

44
Q

Name 4 complicated machines.

A

Cars, tractors, food processors, and areoplanes.

45
Q

Name 6 simple machines.

A

Lever (Most important), inclined plane, wheel and axle, wedge, pulley, and screw.

46
Q

How many classes of levers are there?

A

3.

47
Q

We can group levers into different classes all consisting of the ___, ___, and ____.

A

We can group levers into different classes all consisting of the load, pivot, and effort.

48
Q

Explain first-class lever.

A

The pivot is placed between the effort and the load.

49
Q

Explain second-class lever.

A

The load is between the pivot and the effort.

50
Q

Explain third-class lever.

A

The effort is between the pivot and the load.

51
Q

Kilograms to Newtons.

A

1 Kg = 10 Newtons

52
Q

Newtons to Kilograms.

A

10 Newtons = 1 Kg.

53
Q

What is a lever?

A

A lever is a uniform bar that turns around a pivot (fulcrum) and lifts a weight (load) with one end when pressure (effort) is applied to the other end.

54
Q

What is the name of the perpendicular distance of the load from the fulcrum (pivot)?

A

The perpendicular distance of the load from the fulcrum (pivot) is called the load distance.

55
Q

What is the name of the perpendicular distance of the effort from the fulcrum (pivot)?

A

The perpendicular distance of the effort from the fulcrum (pivot) is called the effort distance.

56
Q

True or False. It is easier to lift the load when the effort distance is longer than the load distance.

A

True.

57
Q

Why are the soles of shoes rough?

A

Soles of shoes are rough, especially in sport’s shoes, to help increase friction and allow the athlete better grip during their activity.

58
Q

Name the 4 directions of a force.

A 
Upward thrust.
Weight (goes downward).
Air friction (Goes west direction).
Engine thrust (goes south direction).
59
Q

Why do we repeat experiments?

A

To make the results more accurate and reliable.

60
Q

How can we make results more reliable?

A

By repeating experiments.

Science 2021. (24 decks)

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