UNIT 3 - Forces and Motion

Forces and Motion Flashcards

Average velocity

The change in displacement over the change in time.

Average acceleration

The change in velocity over the change in time.

Instantaneous velocity

Velocity at a specific moment in time.

Instantaneous acceleration

Acceleration at a specific moment in time.

Velocity (𝑣)

The rate of change of displacement.

Acceleration (𝑎)

The rate of change of velocity.

Free fall

Motion under the force of gravity only.

g

Acceleration due to gravity, approximately 9.81 m/s².

Newton's second law of motion

𝐹 = 𝑚𝑎

Newton’s third law of motion

States that for every action, there is an equal and opposite reaction.

Normal contact force

The perpendicular force exerted by a surface on an object in contact with it.

Friction

A force that opposes motion between surfaces in contact.

Upthrust

An upward force exerted by a fluid that opposes the weight of an immersed object.

Pressure (𝑝)

𝐹/𝐴

Density (𝜌)

Mass per unit volume.

Moment of a force

The turning effect of a force.

Couple

A pair of equal and opposite forces acting on a body but not along the same line.

Torque of a couple

The moment of a couple, calculated as force times the perpendicular distance between the forces.

Centre of mass/gravity

The point at which the entire weight of an object appears to act.

Work done

Work done / energy transferred.

Power

Rate of energy transfer.

Elastic energy

The energy stored in a deformed elastic material.

Elastic limit

The point beyond which a material will be permanently deformed.

Tensile stress (σ)

Force per unit area.

Tensile strain (ε)

Change in length divided by original length.

Ultimate tensile strength

The maximum stress a material can withstand before breaking.

Young modulus (E)

The ratio of stress to strain.

Elastic collision

A collision in which kinetic energy is conserved.

Inelastic collision

A collision in which kinetic energy is not conserved.

Momentum

Mass multiplied by velocity.