Mechanics | Edexcel A-Level Physics (9PH0)

Mechanics

180 questions
17 subtopics
Paper 1: Advanced Physics I
Paper 1 and Paper 3

The core of Paper 1, drawn on again synoptically in Paper 3.

Covers the equations of uniformly accelerated motion and the graphs that go with them, vectors and projectiles, Newton's three laws, momentum, moments and equilibrium, and work, energy and power.

Sample questions from Mechanics

Answer each one closed book first, then open the answer.

The equations of uniformly accelerated motion

Why does s = (u + v)t/2 follow from the definition of average velocity when the acceleration is uniform?

Show the answer
For constant acceleration the average velocity is the mean of the initial and final velocities, and displacement is average velocity multiplied by time.
Scalars and vectors

What are four examples of scalar quantities met in mechanics?

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Mass, energy, speed and time are all scalars.
Projectile motion

What quantity links the horizontal and vertical motions of a projectile?

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The time, which is the same for both motions.
Newton's third law, mass and weight

A ball falls towards the Earth. What is the Newton's third law partner of the Earth's gravitational pull on the ball?

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It is the equal and opposite gravitational pull of the ball on the Earth.
Linear momentum and its conservation

How does conservation of momentum follow from Newton's third law of motion?

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The two interacting bodies exert equal and opposite forces on each other for the same length of time, so they experience equal and opposite changes of momentum which cancel.
The moment of a force

Why is the moment of a force not measured in joules, even though the joule is also a newton metre?

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Work uses the distance moved along the line of action of the force, whereas a moment uses a distance perpendicular to it, so they are different physical quantities.
Work done by a force

Why is no work done by a force that acts at right angles to the motion?

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Because cos 90° = 0, the force has no component along the displacement and so transfers no energy.
Conservation of energy and dissipation

What energy transfers occur as a pendulum bob swings from its highest point down to its lowest point and up again?

Show the answer
Gravitational potential energy is transferred to kinetic energy on the way down and back to gravitational potential energy on the way up, with a small amount transferred to internal energy by air resistance on each swing.

The 17 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
The equations of uniformly accelerated motion	Recall questions on the four suvat equations, when they may be used, which to choose when time is not given, and the sign convention for vertical motion.	19
Displacement-time and velocity-time graphs	Recall questions on what the gradients and areas of motion graphs represent, reading instantaneous velocity from a curve, and recognising non-uniform acceleration.	13
Scalars and vectors	Recall questions on the difference between a scalar and a vector, examples of each, and why distance and displacement, or speed and velocity, are not the same.	8
Resolving vectors and finding resultants	Recall questions on resolving a vector into perpendicular components, combining vectors at right angles and at any angle, and the forces on a body on a slope.	10
Projectile motion	Recall questions on treating horizontal and vertical motion separately, what links them, the velocity at the highest point, and how air resistance changes the range.	8
Free-body diagrams and Newton's first and second laws	Recall questions on what belongs on a free-body diagram, the statements of the first and second laws, the definition of the newton, and applying F = ma.	10
Newton's third law, mass and weight	Recall questions on what a third-law pair shares, why the pair never cancels, gravitational field strength, and the difference between mass and weight.	10
Terminal velocity and measuring g by free fall	Recall questions on how a skydiver's acceleration changes, the shape of the velocity-time graph, and the electromagnet and light-gate determination of g.	10
Linear momentum and its conservation	Recall questions on the definition and unit of momentum, why a direction must be fixed first, and how conservation follows from Newton's laws.	12
Elastic and inelastic collisions in one dimension	Recall questions on what separates an elastic from an inelastic collision, where the lost kinetic energy goes, and how momentum is still conserved when a ball rebounds.	8
The moment of a force	Recall questions on the definition and unit of a moment, why the perpendicular distance is used, and why a moment is not measured in joules.	8
Centre of gravity, equilibrium and the principle of moments	Recall questions on locating a centre of gravity, the two conditions for equilibrium, the principle of moments, and why a low, wide vehicle is stable.	14
Work done by a force	Recall questions on the definition of work and the joule, the cosine term when a force acts at an angle, and what negative work means.	9
Kinetic and gravitational potential energy	Recall questions on the two energy equations, why doubling speed quadruples kinetic energy, and why the potential energy formula only holds near the Earth's surface.	8
Conservation of energy and dissipation	Recall questions on the principle of conservation of energy, why a falling body's speed does not depend on its mass, and why dissipated energy cannot be recovered.	9
Power, and the equation P = Fv	Recall questions on the definition of power and the watt, the derivation of P = Fv, and the driving force needed at constant velocity.	10
Efficiency and wasted energy	Recall questions on efficiency from energies and from powers, why it has no unit, why it can never reach 100%, and the joules in a kilowatt-hour.	14

Mechanics is 180 of the 1,616 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.