Mechanics (AS) Flashcards Preview

AQA A-Level Physics > Mechanics (AS) > Flashcards

Flashcards in Mechanics (AS) Deck (20)
Loading flashcards...
1
Q

I am a quantity with size and direction. What am I?

A

Vector.

2
Q

I am a quantity with size. What am I?

A

Scalar.

3
Q

State Newton’s First Law.

A

The velocity of an object will not change unless a resultant force acts on it.

4
Q

State Newton’s Second Law.

A

Acceleration is proportional to the force.

F = m x a

5
Q

State Newton’s Third Law.

A

If an object A exterts a force on object B, then object B exerts an equal but opposite force on object A.

6
Q

Galileo said: all objects fall at the _____ _____.

A

Galileo said: all objects fall at the (same rate).

A feather takes longer to fall than a brick due to air resistance. In a vaccum, they’d take the same time.

7
Q

When does terminal speed occur?

A

You will reach a terminal speed when

the friction force = the driving force.

8
Q

What is friction?

A

Friction is a force that opposes motion.

There are two types of friction:
‘dry friction’ between solid surfaces and
‘fluid friction’ (known as drag, fluid resistance or air resistance).

9
Q

What do frictional forces convert kinetic energy into?

A

Heat and sound.

10
Q

What is lift?

A

Lift is an upwards force on an object moving through a fluid.

11
Q

When does lift occur?

A

Lift occurs when the shape of an object causes the fluid flowing over it to change direction.

12
Q

In which direction does lift act?

A

The force acts perpendicular to the direction the fluid flows in.

13
Q

What is momentum?

A

momentum = mass x velocity

p (kg/ms) = m (kg) x v (ms^-1)

14
Q

What is a moment?

A

A moment is the turning effect of a force.

M = F x d

Where d is the perpendicular distance from the point to the line of action of the force (in m).

15
Q

What is the principle of moments?

A

For a system to be in equilibrium,

sum of clockwise moments = sum of anticlockwise moments

16
Q

What is a couple?

A

A couple is a pair of forces of equal size which act parallel to each other, but in opposite directions.

17
Q

A couple is a ______ of forces of equal ______ which act ______ to each other, but in ______ ______.

A

A couple is a (pair) of forces of equal (size) which act (parallel) to each other, but in (opposite directions).

18
Q

What is the centre of mass?

A

The centre of mass of an object is the single point that you can consider its whole weight to act through.

19
Q

The centre of mass of an object is the ______ ______ that you can consider its whole ______ to act through.

A

The centre of mass of an object is the (single point) that you can consider its whole (weight) to act through.

20
Q

How can you find the centre of mass of an irregular object?

A
  1. Hang the object freely from one point.
  2. Draw a vertical line downwards.
  3. Hang the object from another point.
  4. Draw another vertical line downwards.

The centre of mass should be where these lines cross.