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GCSE Physics (P3) > Using Physics to Make Things Work > Flashcards

Flashcards in Using Physics to Make Things Work Deck (47)
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1
Q

What is a moment?

A

The turning effect of a force (on an object)

2
Q

What are moments measured in?

A

Newton metres Nm

3
Q

What is the line of action?

A

The line along which a force acts

4
Q

In the equation M = F x d, what does d stand for?

A

The perpendicular distance from the line of action to the pivot. It is measured in metres

5
Q

What can be done to increase the moment?

A

Either:

Increase the force

Increase the distance

6
Q

When using a lever, what is the name of the force we are trying to move?

A

The load

7
Q

When using a lever, what is the name of the force we are applying to the lever?

A

The effort

8
Q

What is mean by a force multiplier?

A

The effort applied is less than the load

9
Q

What is mean by a distance multiplier?

A

A small distance is moved on the load side of the fulcrum and a large distance is moved on the other as a result.

10
Q

What is the centre of mass?

A

The point where an objects mass can be thought to be concentrated

11
Q

If an object is freely suspended where will its centre of mass lie?

A

Directly below the point of suspention

12
Q

What is equilibrium?

A

The state of an object when it is at rest

13
Q

How can you find the centre of mass of a thin, irregular sheet of a material?

A
  • Suspend the shape from a pin held in a clamp stand. Because it is freely suspended it able to turn
  • When it comes to rest, hand a plumbline from the same pin.
  • Mark the position of the plumbline against the sheet
  • Hang the sheet with the pin at another point and repeat.
  • The centre of mass is where the lines that marked the position of the plumbline cross
14
Q

What does the position of the centre of mass depend upon?

A

The shape of the object. Subsequently, it can sometimes lie outside the shape of the object

15
Q

Where does the centre of mass lie in a symetrical object?

A

Along the axis of symmetry. If the object has more than one axis of symmetry, the centre of mass is where the axes meet

16
Q

If an object is in equilibrium, it is…

A

balanced and not turning

17
Q

What is the total clockwise moment equal to (in an object in equilibrium)?

A

The total anti-clockwise moment

18
Q

State some everyday examples of the principle of moments

A

Seesaws and balance scales

19
Q

How is the stability of an object increased?

A

By making its base as wide as possible and its centre of mass as low as possible

20
Q

Where does the line of action of the weight of an object act?

A

Through its centre of mass

21
Q

If the line of action of the weight lies outside the base of an object, what will happen?

A

There will be a resultant moment and the object will tend to topple over (although not always)

22
Q

The wider the object, the lower its centre of mass. This means…

A

the further it has to tilt before the line of action of weight moves outside the base

23
Q

What two things can make an object topple?

A

If the line of action of weight is outside the base

OR

if the resultant moment about its point of turning is not 0

24
Q

What are pascals (Pa) equal to?

A

N/m2

25
Q

In the equaltion P = F/A, what is A?

A

The cross-sectional area at right angles to the direction of the force. It is measured in m2

26
Q

How does the pressure of a fluid act?

A

Equally in all directions

27
Q

Can you compress liquids?

A

No.

28
Q

How do hydraulic systems use pressure?

A

They use the pressure in a fluid to exert a force

29
Q

What does the force exerted by a hydraulic pressure system depend on?

A
  • The force exerted on the system
  • The area of the cylinder on which the force acts upon
  • The area of the cylinder which exerts the force
30
Q

What allows a hydraulic system to act as a force multiplier and what does this mean it can be used to do?

A

Different cross-sectional areas on the effort and load sides of the system.

Therefore, a small effort can be used to move a large load.

31
Q

What causes centripetal acceleration?

A

When an object moves in a circle it is continually changing direction, so it is continuously changing velocity. In other words, it is accelerating.

This acceleration is called the centripetal acceleration.

32
Q

What is centripetal force?

A

The resultant force towards the centre of a circle acting on an object moving in a circular path.

33
Q

What happens if the centripetal force stops acting?

A

The object will continue to move in a straight line at a tangent to the circle.

34
Q

What is centripetal acceleration?

A

The acceleration of an object moving in a circle at a constant speed. It always acts towards the centre of the circle.

35
Q

What causes the centipetal force needed to make an object perform circular motion increase?

A
  • The mass of the object increases
  • The speed of the object increases
  • The radius of the circle decreases
36
Q

Give an example of oscillating motion.

A

A pendulum moving to and fro along the same line

37
Q

Define oscillating motion.

A

The motion of any object that moves to and fro along the same line (like a pendulum).

38
Q

What is a simple pendulum?

A

A pendulum consisting of a small, spherical bob (mass) suspended by a thin string from a fixed point

39
Q

What is the equilibrium position?

A

The position of a pendulum when it stops moving

40
Q

What is a bob?

A

The mass at the end of a pendulum

41
Q

What happens when the bob is displaced to one side (and let go of)

A

The pendulum oscillates back and forth through the equilibrium position

42
Q

What is the amplitude of an oscillation?

A

The time taken for the pendulum to complete one full cycle. This is:

  • The time taken for the bob to go from the highest position on one side to the highest position on the other an back

OR:

  • The time taken between successive passes in the same direction through the equilibrium position.
43
Q

What does the time period of the oscillation depend on?

A

The length of the pendulum

44
Q

How does the length of the pendulum effect the time period of its oscillation?

A

As the length increases, so does the time period

(i.e. bigger pendulums take longer to swing)

45
Q

What is the frequency of oscillations?

A

The number of complete cycles of oscillation per second

46
Q

What is a playground swing an example of?

A

Oscillating motion

47
Q

What happens if a swing is not pushed repeatedly and why?

A

It will come to rest because energy is transfered at the top of the swing due to friction and due to air resistance.