definitions

Question 1

What is a scalar quantity?

Answer 1

A quantity with only magnitude (e.g., distance, speed, mass).

Question 2

What is a vector quantity?

Answer 2

A quantity with both magnitude and direction (e.g., velocity, force).

Question 3

Define speed.

Answer 3

Distance travelled per unit time.

Question 4

Define velocity.

Answer 4

Change in displacement per unit time.

Question 5

Define acceleration.

Answer 5

Change in velocity per unit time.

Question 6

What is deceleration?

Answer 6

Negative acceleration.

Question 7

What is the value of gravitational acceleration (g) near Earth’s surface?

Answer 7

Approximately 9.8 m/s².

Question 8

What is mass?

Answer 8

A measure of the quantity of matter in an object.

Question 9

What is inertia?

Answer 9

The resistance of an object to changes in its state of motion.

Question 10

Define weight.

Answer 10

Force due to gravity on a mass.

Question 11

Define gravitational field strength.

Answer 11

Force per unit mass (g = W/m).

Question 12

Define density.

Answer 12

Mass per unit volume (ρ = m/V).

Question 13

What is a resultant force?

Answer 13

The single force representing the vector sum of all forces acting on an object.

Question 14

State Newton’s First Law.

Answer 14

An object remains at rest or in uniform motion unless acted upon by a resultant force.

Question 15

State Newton’s Third Law.

Answer 15

When one body exerts a force on another, the second body exerts an equal and opposite force.

Question 16

What is friction?

Answer 16

A force that opposes motion between two surfaces in contact.

Question 17

Define spring constant.

Answer 17

Force per unit extension (k = F/x).

Question 18

Define moment of force.

Answer 18

Force × perpendicular distance from the pivot.

Question 19

What is the centre of gravity?

Answer 19

The point through which the entire weight of a body acts.

Question 20

Define momentum.

Answer 20

Mass × velocity (p = mv).

Question 21

Define impulse.

Answer 21

Force × time (Impulse = Δp).

Question 22

Define kinetic energy.

Answer 22

½ × mass × velocity² (Ek = ½mv²).

Question 23

Define gravitational potential energy.

Answer 23

mass × gravity × height (Ep = mgh).

Question 24

Define work.

Answer 24

Force × distance moved in the direction of the force (W = Fd).

Question 25

Define power.

Answer 25

Work done or energy transferred per unit time (P = W/t or P = E/t).

Question 26

Define efficiency.

Answer 26

(useful energy ÷ total energy) × 100%.

Question 27

Define pressure.

Answer 27

Force per unit area (p = F/A).

Question 28

State the hydrostatic pressure formula.

Answer 28

Δp = ρgΔh.

Question 29

What is absolute zero?

Answer 29

−273°C, where particles have minimum kinetic energy.

Question 30

Define specific heat capacity.

Answer 30

Energy required to raise the temperature of 1 kg of a substance by 1°C.

Question 31

Define latent heat.

Answer 31

Energy required to change the state of a substance without a change in temperature.

Question 32

Define frequency.

Answer 32

Number of waves passing a point per second (Hz).

Question 33

Define wavelength.

Answer 33

Distance between two consecutive identical points on a wave.

Question 34

Define amplitude.

Answer 34

Maximum displacement from the mean position.

Question 35

State the wave speed formula.

Answer 35

v = fλ (wave speed = frequency × wavelength).

Question 36

Define refractive index.

Answer 36

n = sin i / sin r.

Question 37

Define critical angle.

Answer 37

The angle of incidence for which the angle of refraction is 90°.

Question 38

Define magnification.

Answer 38

Magnification = image height ÷ object height.

Question 39

What is the speed of electromagnetic waves in a vacuum?

Answer 39

3.0 × 10⁸ m/s.

Question 40

Define electric current.

Answer 40

Charge per unit time (I = Q/t).

Question 41

Define potential difference (voltage).

Answer 41

Work done per unit charge (V = W/Q).

Question 42

Define resistance.

Answer 42

Voltage divided by current (R = V/I).

Question 43

Define e.m.f. (electromotive force).

Answer 43

Electrical work done by a source per unit charge (E = W/Q).

Question 44

State Ohm’s Law.

Answer 44

Current is directly proportional to voltage at constant temperature.

Question 45

State the formula for electrical power.

Answer 45

P = IV.

Question 46

State the formula for electrical energy.

Answer 46

E = IVt.

Question 47

What is a kilowatt-hour (kWh)?

Answer 47

A unit of electrical energy equal to using 1000 watts for 1 hour.

Question 48

Define proton number.

Answer 48

Number of protons in the nucleus (Z).

Question 49

Define nucleon number.

Answer 49

Total number of protons and neutrons (A).

Question 50

What is an isotope?

Answer 50

Atoms of the same element with different numbers of neutrons.

Question 51

Define half-life.

Answer 51

Time taken for half the radioactive nuclei in a sample to decay.

Question 52

What is an alpha particle?

Answer 52

A helium nucleus (2 protons and 2 neutrons).

Question 53

What is a beta particle?

Answer 53

A high-speed electron from the nucleus.

Question 54

What is gamma radiation?

Answer 54

High-frequency electromagnetic wave emitted from a nucleus.