UNIT 3

Question 1

Vector Impact

Answer 1

the velocity of a projectile immediately before striking the ground

Question 2

Resolution

Answer 2

determining the components of a vector, usually at right angles to each other

Question 3

Force

Answer 3

a push or pull between objects, which may cause one or both objects to change speed and/or the direction of their motion (i.e. accelerate) or change their shape

Question 4

weight

Answer 4

a measure of the force of gravity acting on an object

Question 5

Mass

Answer 5

an object’s resistance to a change in motion; also commonly stated as the amount of matter in an object (symbol: m; SI unit: kilogram; unit symbol: kg)

Question 6

Friction

Answer 6

is the resistance to motion of two surfaces moving relative to another. It is the result of the electromagnetic attraction between the charged particles in two touching surfaces

Question 7

uniform circular motion

Answer 7

the motion of an object travelling at a constant speed in a circle

Question 8

centripetal force

Answer 8

the force acting on an object travelling in a circle that constantly acts on an object towards the centre of motion (symbol: Fc ; SI unit: newton; unit symbol: N)

Question 9

centripetal acceleration

Answer 9

the acceleration experienced by any object moving in a circular path directed towards the centre of motion (symbol: ac; SI unit: metres per second squared; unit symbol: m s–2)

Question 10

rotational speed

Answer 10

the number of revolutions an object does per second, as distinguished from the term ‘average speed’, which is the linear speed.

Question 11

Newton’s law of universal gravitation

Answer 11

states that the force of attraction between each pair of point particles is directly proportional to the product of their masses and inversely proportional to the square of the distance between them

Question 12

The first law of planetary motion (law of orbits)

Answer 12

states that all planets move about the Sun in elliptical orbits that have the Sun as one of the foci

Question 13

Kepler’s second law of planetary motion (the law of areas)

Answer 13

states that a radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time.

Question 14

The third law of planetary motion (law of periods)

Answer 14

states that the square of the sidereal periods of a planet is directly proportional to the cube of its mean distance from the Sun: T² ∝ r³.

Question 15

Electric field

Answer 15

a region of space near an electrically charged particle or object within which a force would be exerted on other electrically charged particles or objects

Question 16

Uniform electric field

Answer 16

a field that has constant field strength, as found between charged parallel plates.

Question 17

Electrical potential energy

Answer 17

the capacity of electric charge carriers to do work due to their position in an electric field

Question 18

Electric potential

Answer 18

the electrostatic potential energy stored per unit charge at any given
point (symbol: V; SI unit: volt; unit symbol: V)

Question 19

The electrical potential difference

Answer 19

the work done in moving a unit charge between the final and the initial positions in an electric field (symbol: V; SI unit: volt; unit symbol: V)

Question 20

Magnetic field

Answer 20

a region of space where a magnetic force is experienced.

Question 21

solenoid

Answer 21

a long straight coil of wire used to generate a controlled and almost uniform magnetic field

Question 22

magnetic flux

Answer 22

a measurement of the total magnetic field that passes through a given area; a measure of the number of magnetic field lines passing through the given area (symbol: Φ; SI unit: weber; unit symbol: Wb).

Question 23

magnetic flux density

Answer 23

the strength of a magnetic field or the number of magnetic field lines per unit area (symbol: B; SI unit: weber per square metre; unit symbol: Wb m–2 or T)

Question 24

electromagnetic induction

Answer 24

the production of an electromotive force (EMF) or voltage across an electrical conductor due to its dynamic interaction with a magnetic field

Question 25

electromotive force

Answer 25

(EMF) a difference in potential that tends to give rise to an electric current: it is measured in volts (V)

Question 26

Faraday’s law

Answer 26

law stating that when the magnetic flux linking a circuit changes, an electromotive force (EMF) is induced in the circuit proportional to the rate of change of the flux linkage

Question 27

Lenz’s law states

Answer 27

‘The direction of an induced electric current always opposes the change in the circuit or the magnetic field that produces it.’

Question 28

The law of conservation of energy:

Answer 28

‘The total energy of a system remains constant; energy can neither be created nor destroyed, rather, it transforms from one form to another.’

Question 29

What is mutual induction

Answer 29

the production of an EMF in a circuit by a change of current in an adjacent circuit that is linked to the first by the flux lines of the magnetic field

Question 30

What is the difference between a step-down and step up transformer

Answer 30

• A step-down transformer is when the primary voltage is larger than the secondary
• A step-up transformer is when the secondary voltage is larger than the primary voltage