P3 - Using Physics Flashcards

1
Q

What is the moment of a force?

A

A measure of the turning effect of a force on an object.

2
Q

How is the moment of a force calculated?

A

force x perpendicular distance from the line of action of the force to the pivot

3
Q

Give two ways in which the moment of a force can be increased.

A
• Increase the force

- Increase the perpendicular distance

4
Q

What is the centre of mass of an object?

A

The point where its mass is concentrated.

5
Q

Where is the centre of mass of an object that is suspended from a fixed point?

A

The centre of mass is directly beneath the point of suspension.

6
Q

Where is the centre of mass of a symmetrical object?

A

Along the axis of symmetry.

7
Q

What is the relationship between the moments of the forces acting on an object that isn’t turning?

A

The sum of anticlockwise moments = The sum of clockwise moments (ie. W1d1 = W2d2)

8
Q

How is the weight of the first object calculated with moments?

A

W1 = W2d2 / d1

9
Q

Give three ways in which an object can be made more stable.

A
• Increasing the width of the base.
• Making the centre of mass lower.
• Bolting the object to the floor.
10
Q

What will make a body topple over when tilted?

A

If the line of action of its weight is outside its base.

11
Q

What are the moments of the forces when an object topples over?

A

The resultant moment about the point of turning is not zero.

12
Q

What is pressure?

A

Force divided by the area which the force acts on.

13
Q

What is the unit of pressure?

A

The Pascal, Pa. (1 N/m2)

14
Q

What happens to the pressure in a fluid?

A

The pressure acts equally in all directions.

15
Q

How does a hydraulic pressure system work?

A
• Hydraulic fluid into the upper or lower part of a chamber to make the piston move in or out of the cylinder.
• The force exerted is transmitted to other parts of the system.
16
Q

Why are liquids used in hydraulic systems?

A
• Liquids are virtually incompressible so the volume doesn’t change.
• The whole force can be transmitted to the other parts.
17
Q

How does a hydraulic car jack work?

A
• The handle being pressed down forces hydraulic fluid out of a narrow cylinder into a wide cylinder.
• The pressure of the fluid forces the piston in the wider cylinder outwards.
• The piston forces the pivoted lever to raise the car.
18
Q

Why is the second force in a hydraulic car jack greater?

A

The area of the piston is greater.

19
Q

How can an object moving at a constant speed be accelerating?

A

If the motion is circular.

20
Q

Why is an object moving in a circular motion said to be accelerating?

A
• Velocity is dependent on direction as is acceleration.

- The velocity is changing as the direction is changing.

21
Q

What is centripetal acceleration?

A

The acceleration towards the centre of the circle of an object that is moving round the circle.

22
Q

What does the centripetal force depend on?

A
• Mass
• Speed
23
Q

What is centripetal force?

A

The name of a resultant force acting on a circle moving round an object.

24
Q

What affects the time period of a pendulum?

A

Its length.

25
Q

How is the time period of a pendulum measured accurately?

A

The average time of 20 oscillations.

26
Q

How is a playground swing different to a pendulum?

A
• Friction at the top of the swing slows it.

- Air resistance slows it.

27
Q

What is the equilibrium position of a pendulum?

A

The point at which the pendulum is fastest and nearest the ground.

28
Q

What is the amplitude of an oscillating object?

A

The distance from the equilibrium position to its highest point.

29
Q

What is the time period of a pendulum?

A

-The time to one of the highest points and back.
or
-The time between successive passes in the same direction through the equilibrium.