Teaching Newton's Laws

Unit 2.2

When is it helpful to say that forces always come in pairs? What are the benefits of changing the order of teaching Newton’s Laws? How do we cope with the terminology of net force, resultant force, total force, balanced forces, equal and opposite forces? Is gravitational force better than weight? Which is the best practical sim for the students to use when investigating the terminal speed of a falling object?

The concept of inertia, that mass is an expression of the inertia of a body

Newton's first law of motion and be able to state it

how unbalanced forces produce a change in a body's motion and that the acceleration of a body is directly proportional to the resultant force and inversely proportional to the body's mass

Newton's second law of motion, and be able to state it, in the form: resultant force = mass × acceleration; F = ma

the distinction between the weight and mass of an object, the approximation that the weight of an object of mass 1 kg is 10 N on the surface of the Earth and use data on gravitational field strength in calculations involving weight

(W = mg) and gravitational potential energy

weight (N) = mass (kg) × gravitational field strength (N/kg)

forces and their effects to explain the behaviour of objects moving through the air, including the concept of terminal speed

Newton's third law of motion and be able to state it

• Investigation of the terminal speed of a falling object