(c) Forces, movement, shape and momentum

Describe the effects of forces between bodies such as changes in speed, shape or direction

Identify different types of force such as gravitational or electrostatic

Understand how vector quantities differ from scalar quantities

Understand that force is a vector quantity

Calculate the resultant force of forces that act along a line

Know that friction is a force that opposes motion

Know and use unbalanced force = mass × acceleration, F = ma.

Know and use weight = mass × gravitational field strength, W = mg.

Know that the stopping distance of a vehicle is made up of the sum of the thinking distance and the braking distance

Describe the factors affecting vehicle stopping distance, including speed, mass, road condition and reaction time

Describe the forces acting on falling objects (and explain why falling objects reach a terminal velocity)

Practical: investigate how extension varies with applied force for helical springs, metal wires and rubber bands

Know that the initial linear region of a force-extension graph is associated with Hooke’s law

Describe elastic behaviour as the ability of a material to recover its original shape after the forces causing deformation have been removed

Know and use momentum = mass × velocity, p = mv.

Use the idea of momentum to explain safety features

Use the conservation of momentum to calculate the mass, velocity or momentum of objects

Use force = change in momentum ÷ time taken, F = Δp/t = (mv − mu)/t.

Demonstrate an understanding of Newton’s third law

Know and use moment = force × perpendicular distance from the pivot.

Know that the weight of a body acts through its centre of gravity

Use the principle of moments for a simple system of parallel forces acting in one plane

Understand how the upward forces on a light beam, supported at its ends, vary with the position of a heavy object placed on the beam