Mocks Science 1 definitions

Normal force

The force or the component of a force which a surface exerts on an object with which it is in contact, and which is perpendicular to the surface.

Frictional force

The force that opposes the motion of an object and which acts parallel to the surface.

Static frictional force

The force that opposes the tendency of motion of a stationary object relative to a surface.

Kinetic frictional force

The force that opposes the motion of a moving object relative to a surface

Weight

The gravitational force the Earth exerts on any object on or near its surface

State Newton's first law of motion

A body will remain in its state of rest or motion at constant velocity unless a non-zero resultant/net force acts on it.

State Newton's second law of motion

When a net force acts on an object, the object will accelerate in the direction of the force and the acceleration is directly proportional to the force and inversely proportional to the mass of the object.

State Newton's third law of motion

When object A exerts a force on object B, object B SIMULTANEOUSLY exerts an oppositely directed force of equal magnitude on object A

State Newton's Law of Universal Gravitation

Each body in the universe attracts every other body with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.

State Newton's second law of motion in terms of momentum

"The net (or resultant) force acting on an object is equal to the rate of change of momentum of the object in the direction of the net force."

Free fall

Motion during which the only force acting on an object is the gravitational force

Projectile

A object which has been given an initial velocity and then it moves under the influence of the gravitational force only

Momentum

The product of an object's mass and its velocity.

Impulse

The product of the resultant/net force acting on an object and the time the net force acts on the object.

A isolated system

It is a system on which the resultant/net external force is zero

Elastic collision

It is a collision in which the total momentum and total kinetic energy is conserved

Inelastic collision

It is a collision in which the total momentum and total kinetic energy is not conserved

State the principle of conservation of linear momentum

The total linear momentum of an isolated system remains constant (is conserved).

Work done on an object by a constant force

"FΔx cos θ , where F is the magnitude of the force, Δx the magnitude of the displacement and θ the angle between the force and the displacement."

Conservative force

A force for which the work done in moving an object between two points is independent of the path taken.

Non - conservative force

A force for which the work done in moving an object between two points depends on the path taken.

Power

The rate at which work is done or energy is expended

State the work-energy theorem

The work done on an object by a net force is equal to the change in the object's kinetic energy OR the work done on an object by a net force is equal to the change in the object's kinetic energy

State the principle of conservation of mechanical energy

The total mechanical energy (sum of gravitational potential energy and kinetic energy) in an isolated system remains constant.

State the meaning of an isolated system

A system is isolated when the net external force (excluding the gravitational force) acting on the system is zero.

State the Doppler effect

The change in frequency (or pitch) of the sound detected by a listener, because the sound source and the listener have different velocities relative to the medium of sound propagation.

Electric field at a point

The electric field at a point is the electrostatic force experienced per unit positive charge placed at that point.

Electric field

The region of space in which an electric charge experiences a force.

State Coulomb's law

The magnitude of the electrostatic force exerted by one point charge (Q1) on another point charge (Q2) is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance (r) between them

One coulomb

The charge transferred in a conductor in one second if the current is one ampere.

Emf

The maximum energy provided by a battery per unit charge passing through it.

State Ohm's law in words

The potential difference across a conductor is directly proportional to the current in the conductor at constant temperature.

Power

The rate at which work is done or energy is expended

Potential difference

The potential difference across the ends of a conductor is the energy transferred per unit electric charge flowing through it.

Terminal potential difference

The voltage measured across the terminals of a battery when charges are flowing in the circuit.

Current strength

The rate of flow of charge.

Resistance

The ratio of the potential difference across a resistor to the current in the resistor.

One ohm

One ohm (Ω) is equal to one volt per ampere.

Internal resistance

The resistance within a battery when current is flowing which causes a decrease in the potential difference that the battery can supply to the external circuit.

rms potential difference

The AC potential difference which dissipates/produces the same amount of energy as an equivalent DC potential difference.

rms current

The alternating current which dissipates/produces the same amount of energy as an equivalent direct current

Photoelectric effect

The process whereby electrons are ejected from a metal surface when light of suitable frequency is incident on that surface.

Threshold frequency

The minimum frequency of light needed to emit electrons from a certain metal surface.

Work function

The minimum energy that an electron in the metal needs to be emitted from the metal surface.

Atomic absorption spectum

An atomic absorption spectrum is formed when certain frequencies of electromagnetic radiation that passes through a medium, e.g. a cold gas, is absorbed

Atomic emission spectrum

An atomic emission spectrum is formed when certain frequencies of electromagnetic radiation are emitted due to an atom's electrons making a transition from a high-energy state to a lower energy state.