Year 12 physics definitions topic order

Question 1

Scalar

Answer 1

A scalar quantity is one which has magnitude but not direction.

Question 2

Vector

Answer 2

A vector quantity is one which has both magnitude and direction.

Question 3

Vector triangle

Answer 3

A vector triangle is a type of scale diagram with two vectors drawn tip-to-tail, to show how they can be added together.

Question 4

Resultant vector

Answer 4

The vector sum of two or more vectors.

Question 5

The components of a vector

Answer 5

The components of a vector are the parts of a vector in two perpendicular directions.

Question 6

One Newton

Answer 6

One Newton is the force needed to give a mass of 1 kg an acceleration of 1 metre per second squared.

Question 7

Equilibrium

Answer 7

Objects are in equilibrium when all the forces acting on them in the same plane (coplanar forces) are balanced - there is zero net or resultant force.

Question 8

The moment of a force

Answer 8

The moment of a force (or turning moment) is the product of the force and the perpendicular distance of its line of action from the pivot or axis.

Question 9

The principle of moments

Answer 9

The principle of moments states that for an object to be in rotational equilibrium, the sum of the clockwise moments must equal the sum of the anti-clockwise moments.

Question 10

Torque

Answer 10

Torque is the moment of a couple. The torque of a couple is the product of one of the forces and the perpendicular distance between them.

Question 11

Centre of mass

Answer 11

The centre of mass of an object is the single point at which all of the mass of the object can be assumed to be situated.

Question 12

Density

Answer 12

The density of an object is its mass per unit volume.

Question 13

Archimedes’ principle

Answer 13

Archimedes’ principle states that the upward buoyant force (upthrust) exerted on an object immersed in a fluid is equal to the weight of the fluid displaced.

Question 14

Work done

Answer 14

The work done, or energy transferred, is the product of the force and the distance moved by the force in the direction of movement.

Question 15

A closed system.

Answer 15

A closed system is any system in which all the energy transfers are accounted for.

Energy or matter cannot enter or leave a closed system.

Question 16

The principle of conservation of energy

Answer 16

The principle of conservation of energy states that the total energy of a closed system remains constant. Energy cannot be created or destroyed, it can only be transferred from one form to another.

Question 17

Elasticity

Answer 17

Elasticity is the property of a body to resume its original shape or size once ethe deforming force or stress has been removed.

Question 18

Hooke’s Law

Answer 18

Hooke’s Law states that the extension of an object is proprtional to the force that causes it, provided that the elastic limit is not exceeded.

Question 19

Stress

Answer 19

Stress is force per unit cross-sectional area. It has unit Nm^-2 or Pa and the symbol σ

Question 20

Strain

Answer 20

Strain is extension per unit length. It has units and is therefore dimensionless.

Question 21

Ductile

Answer 21

A ductile material can be drawn into wires and will show plastic deformation under tensile stress before breaking.

Question 22

Malleable

Answer 22

A malleable material can be hammered or beaten into flat sheets and will show extensive plastic deformation when subject to compressive forces.

Question 23

Brittle

Answer 23

A brittle material will break with little or know plastic deformation.

Question 24

Hard

Answer 24

A hard material will resist plastic deformation by surface indentation or scratching.

Question 25

Stiffness

Answer 25

Stiffness is the ability of a material to resist a tensile force.

Question 26

Polymer

Answer 26

A polymer is a material made of long chains of molecules.

Question 27

Ultimate tensile strength

Answer 27

Ultimate tensile strength is the maximum stress a material can withstsnad while being pulled or stretched, before it fails or breaks.

Question 28

Young modulus

Answer 28

The Young modulus is the ratio of stress/strain for a given material.

Question 29

Newton’s first law

Answer 29

A body will remain at rest or continue to move in a straight line at a constant velocity unless an external force acts on it.

Question 30

Newton’s second law

Answer 30

The resultant force on an object is proportional to the rate of change of momentum of the object, and the momentum change takes place in the direction of the force.

Question 31

Newton’s third law

Answer 31

If object A exerts a force on object B, then object B will exert an equal and opposite force on object A.

Question 32

Impulse

Answer 32

Impulse is the product of force and the the time for which the force acts.

Question 33

Elastic collision

Answer 33

An elastic collision is one in which both the momentum and kinetic energy are conserved. No energy is transferred to other forms.

Question 34

Inelastic collision

Answer 34

An inelastic collision is one in which the momentum is conserved but some of the kinetic energy is transferred to other forms.