Physics exam revision

Question 1

What is displacement?

Answer 1

Is a distance in a given direction

Question 2

What is a vector?

Answer 2

Is a physical quantity that has a magnitude and a direction. e.g: force, acceleration, and velocity.

Question 3

What is a scaler?

Answer 3

A physical quantity which has only a magnitude but no direction. e.g: Energy, time and mass.

Question 4

What is a force?

Answer 4

A force is a push or a pull that acts on an object because of its interaction with another object.

Question 5

What is a contact force?

Answer 5

A contact force is when two objects interact with each other by touching. e.g: air resistance, tension and normal contact forces.

Question 6

What is a non contact force?

Answer 6

A force that interacts with another object at a distance. e.g : gravitational force, magnetic force and electrostatic force.

Question 7

What is Newton’s third law of motion?

Answer 7

When two objects interact with each other they exert an equal amount of force on each other.

Question 8

What is a resultant force?

Answer 8

Total amount of force acting on an object.

Question 9

What do we say when the resultant force is zero?

Answer 9

The forces acting on the object are balanced.

Question 10

What is Newton’s first law of motion?

Answer 10

if the forces acting on the object are balanced:
1. if the object is at rest it stays stationary
2. if the object is moving it keeps moving with the same speed and in the same direction.
If only 2 forces act on each other with zero resultant force, the forces must be equal to each other and act in opposite directions.

Question 11

If an object is acted on by two unequal forces acting in opposite directions the resultant force is:

Answer 11

1. Equal to the difference between the two forces
2. Moves in direction of the larger force

Question 12

If two forces act in the same direction the resultant force is:

Answer 12

The sum of the two forces and is in the same direction.

Question 13

What is a moment?

Answer 13

The turning effect of force on an object.

Question 14

What’s the formula for moment?

Answer 14

M = F x D

Question 15

What are force multipliers?

Answer 15

Using something to move a load which is much larger compared to the effort being put in.

Question 16

The moment of force can be increased by:

Answer 16

1. Increasing the size of the force
2. Increasing the distance between the pivot and the point of force.

Question 17

What is the use of the lever?

Answer 17

The lever is used to increase the size of a force acting on an object.

Question 18

What is the use of the gear?

Answer 18

To transmit the rotational effect of a force.

Question 19

If an object is balanced:

Answer 19

Sum of anticlockwise moments about the pivot = sum of clockwise moments about that pivot.

Question 20

Formula for moments and equilibrium.

Answer 20

W1 x d1 = W2 x d2

Question 21

Why are substances radioactive?

Answer 21

Substances which are radioactive have unstable nucleuses and becomes stable or less stable by emitting alpha, beta or gamma radiation.

Question 22

What is alpha radiation and its relative charge?

Answer 22

Its two protons and two neutrons and has a relative charge of +2

Question 23

What is beta radiation and what is its relative charge?

Answer 23

Its fast moving electrons and has a relative charge of -1

Question 24

What is gamma radiation and what’s it’s relative charge?

Answer 24

It is electromagnetic radiation and has no charge.

Question 25

What is radioactive decay?

Answer 25

An unstable nucleus becomes more stable by emitting an alpha, beta or gamma particle.

Question 26

When an unstable nucleus emits an alpha particle:

Answer 26

1. Its atomic number goes down by two, and its mass number goes down by four. 2. The mass and the charge of the nucleus are both reduced.

Question 27

Why are beta particles emitted?

Answer 27

A beta particle is an electron created and emitted by a nucleus that has too many neutrons compared with its protons.

Question 28

When an unstable nucleus emits a beta particle:

Answer 28

1. The atomic number of the nucleus goes up by 1, and its mass number is unchanged( because neutron changes into a proton.) 2. The charge of the nucleus is increased and the mass if the nucleus is unchanged.

Question 29

When an unstable nucleus emits a gamma particle:

Answer 29

A ray of electromagnetic radiation is released. Neutron emission can occur as a result of alpha colliding with unstable nuclei in the substance. Such a collision can cause the nuclei to become even more unstable and emit a neutron. Because the emitted neutrons are uncharged they can pass through substances more than an alpha and b particle can.

Question 30

What can be used to measure a substances radioactivity?

Answer 30

A Geiger counter

Question 31

Why is radioactive substances dangerous?

Answer 31

1. The radiation can knock electrons out of atoms. The atoms become charged because they lose electrons. This process is called ionisation. When an object is exposed to ionisation it is said to be irradiated but it does not become radioactive. 2. Radioactive contamination - unwanted presence of material containing radioactive atoms on other materials.

Question 32

Workers who use ionising radiation by:

Answer 32

1. Keeping as far away as possible from the source of radiation. 2. Spending as little time as possible in at-risk areas. 3. Sheilding themselves by staying behind thick concrete barriers or lead plates.