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IGCSE Physics Definitions – Forces and Motion

Last updated on April 12th, 2021 at 09:51 am

IGCSE Physics Definitions from the Forces and Motion chapter are listed below. It contains definitions for vector, scalar, torque, CG, velocity, force, acceleration, and important laws like Newton’s laws of motion, Hooke’s law, etc.

This post also includes reference links to detailed posts on respective topics that would certainly help the students of all boards including IGCSE (International General Certificate of Secondary Education), ICSE, CBSE, GCSE, and Leaving Certificate.

IGCSE Physics – Definitions – Forces and Motion

Scalar – A scalar is a quantity that has magnitude only.

Vector – A vector is a quantity that has magnitude and direction. [ Reference: Vector Physics ]

The moment (or torque) of a force -The turning effect of a force (or moment or torque) about a point is defined as the force x the perpendicular distance from the point to the line of action of the force, i.e. moment of force or torque = F × d.
UNIT: Nm. [ Reference: Torque ]

The principle of moments – For a system to be in equilibrium, the sum of anticlockwise moments about a point = the sum of clockwise moments about the same point. [ Reference: Principle of Moments ]

Centre of gravity – The center of gravity is the single point within a body at which the entire weight of the body is considered to act. [ Reference: CG ]

Displacement – The displacement of a point B from point A is the shortest distance from A to B, together with the direction.
UNIT: m. [ Reference: displacement ]

Average speed
Average Speed = total distance traveled ÷ total time taken
UNIT: m/s
[Reference: Average speed]

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Instantaneous Speed
Instantaneous speed is the magnitude of instantaneous velocity and so can never be negative.

UNIT: m/s.
{Reference: Instantaneous speed]

Average Velocity
Average velocity = total displacement ÷ total time taken
UNIT: m/s

Velocity The velocity of a body is the rate of change of displacement. UNIT: m/s. [by velocity we actually mean instantaneous velocity]

Instantaneous velocity: The instantaneous velocity is the ratio of displacement and the time duration provided the time duration is very small (Infinitesimal with time duration approaching zero).
[Reference: Instantaneous Velocity]

Acceleration: Acceleration of a body is its rate of change of velocity. UNIT: m/s^2

Average acceleration = change in velocity ÷ time taken
UNIT: m/s^2

Momentum: The momentum of an object is its mass multiplied by its velocity. (p = mv). It is a vector.
UNIT: kg m/s
[ Reference: Momentum ]

Newton’s Laws of Motion.
1st Law
An object continues in a state of uniform motion in a straight line or remains at rest unless acted upon by a resultant
2nd Law
The rate of change of momentum of an object is proportional to the resultant force acting on it and takes place in the
the direction of that force.
3rd Law
If an object A exerts a force on a second object B then B must exert a force that is equal in magnitude but opposite in direction on A.

Elastic collision: A collision in which there is no loss of kinetic energy. [ Reference: collision ]

Inelastic collision. A collision in which kinetic energy is lost. [ Reference: collision ]

Work: Work done by a force is the product of the magnitude of the force and the distance moved in the direction of the force
UNIT: joule (J) [= Nm]
[ Reference: Work ]

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Energy: The energy of a body or system is the amount of work it can do. UNIT: joule (J).
[Ref: Energy ]

This is the work done per second, or energy converted or transferred per second.
UNIT: watt (W) [= J/s].

Law of Conservation of energy Energy cannot be created or destroyed, only transformed from one form to another.
[ Reference: Law of Conservation of energy]

Gravitational potential energy: This is the energy possessed by virtue of position.
Gravitational PE = mgh
{ Reference: Gravitational PE ]

Terminal Velocity: The terminal velocity is the constant, maximum velocity of an object when the resistive forces on it are equal and
opposite to the accelerating forces (e.g. pull of gravity).
[ Reference: Terminal Velocity ]

Extension = Stretched length – Original length

Hooke’s Law: The extension of an elastic object such as a wire or spring is proportional to the stretching force, provided the extension is not too large. (F = kx).
[Reference: Hooke’s law]

Spring Constant The spring constant (k) is the force per unit extension. UNIT: N/m
[ Reference: Spring]

Efficiency = Useful output work or energy ÷ Input work or energy

Take Away

Hope this post and all the reference links inside the content would help the global students of IGCSE (International General Certificate of Secondary Education), ICSE, CBSE, GCSE, and Leaving Certificate to understand the definitions of the Force and Motion chapter in Physics.

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