State Newton's second law.

The resultant force on a particle is F=ma, in the direction of the acceleration.

State Newton's third law.

If A exerts a force on B, B exerts an equal and opposite force on A.

What is the weight of a mass m?

W=mg, with g=9.8 m s⁻², acting downwards.

What does a zero resultant force imply?

Constant velocity, or rest: the particle is in equilibrium.

Do Newton's third law force pairs cancel?

No, they act on different bodies.

Does a smooth horizontal plane exert friction?

No; only a normal reaction acts, perpendicular to the plane.

What does a light string imply?

Negligible mass, so the tension is the same throughout.

How do you find acceleration from force written as a\mathbf{i}+b\mathbf{j}?

Divide each component by the mass: \mathbf{a}=\mathbf{F}/m.

State the vector forms of constant acceleration formulae.

\mathbf{v}=\mathbf{u}+\mathbf{a}t and \mathbf{r}=\mathbf{u}t+\frac12\mathbf{a}t^2

What is speed in terms of velocity?

The magnitude of the velocity vector.

A lift accelerates upwards: how does R compare with the passenger's weight?

R=mg+ma, so it is greater than the weight.

Newton's laws of motionEdexcel International A Level Maths: Flashcards

Card 1 of 140 of 14 known

Question

State Newton's first law.

Tap or press Space to reveal

Tap card or press Space to flip

See all 14 cards

State Newton's first law.: A particle stays at rest or moves with constant velocity unless a resultant force acts on it.
State Newton's second law.: The resultant force on a particle is $F=ma$ , in the direction of the acceleration.
State Newton's third law.: If A exerts a force on B, B exerts an equal and opposite force on A.
What is the weight of a mass $m$ ?: $W=mg$ , with $g=9.8$ m s⁻², acting downwards.
Express the newton in base units.: kg m s⁻²
What does a zero resultant force imply?: Constant velocity, or rest: the particle is in equilibrium.
Do Newton's third law force pairs cancel?: No, they act on different bodies.
Does a smooth horizontal plane exert friction?: No; only a normal reaction acts, perpendicular to the plane.
What does a light string imply?: Negligible mass, so the tension is the same throughout.
How do you find acceleration from force written as $a\mathbf{i}+b\mathbf{j}$ ?: Divide each component by the mass: $\mathbf{a}=\mathbf{F}/m$ .
Find the magnitude of $3\mathbf{i}-4\mathbf{j}$ .: $\sqrt{3^2+4^2}=5$
State the vector forms of constant acceleration formulae.: $\mathbf{v}=\mathbf{u}+\mathbf{a}t$ and $\mathbf{r}=\mathbf{u}t+\frac12\mathbf{a}t^2$
What is speed in terms of velocity?: The magnitude of the velocity vector.
A lift accelerates upwards: how does $R$ compare with the passenger's weight?: $R=mg+ma$ , so it is greater than the weight.

Exam questions on Newton's laws of motion

A lift of mass $400$ kg carries a passenger of mass $70$ kg. The lift moves vertically upwards with constant acceleration $0.6$ m s⁻² and is supported by a vertical cable. Take $g=9.8$ m s⁻².
Find the tension in the cable.2 marks
A particle $P$ of mass $3$ kg moves on a smooth horizontal plane under the action of two forces, $(5\mathbf{i}-2\mathbf{j})$ N and $(-\mathbf{i}+8\mathbf{j})$ N, only. The vectors $\mathbf{i}$ and $\mathbf{j}$ are perpendicular unit vectors in the plane.
The particle is at rest at time $t=0$ . Find the speed of $P$ when $t=3$ s.2 marks
A crate of mass $15$ kg is pulled along a horizontal floor by a rope inclined at $30^\circ$ above the horizontal. The tension in the rope is $60$ N and the resistance to the motion of the crate is constant at $20$ N. Model the crate as a particle and take $g=9.8$ m s⁻².
Find the acceleration of the crate.3 marks

See the full worksheet

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).