Newton's third law, pulleys and connected particlesAQA A-Level Maths: Flashcards

What these 13 flashcards ask

State Newton's third law.
Do third-law pairs cancel each other?
Properties of a light inextensible string?
What does a smooth pulley tell you about the tension?
Equations for particles A (3 kg) and B (5 kg) over a pulley?
Acceleration of a hanging pair of masses m1<m2?
Force of a string on a pulley with two vertical strings?
Force on a pulley with a horizontal and a vertical string, each tension T?
How can you find the acceleration of connected particles quickly?
How do you find a tension?
Weight component along a smooth plane at \alpha?
What happens to the tension when the string goes slack?
What happens to a particle's equation if a resultant force is zero?

Exam questions on Newton's third law, pulleys and connected particles

A car of mass $1200$ kg tows a trailer of mass $400$ kg along a straight, level road, using a light horizontal tow bar. The driving force on the car is $2400$ N. Resistances to motion are negligible.
Use Newton's third law to describe the force the trailer exerts on the tow bar.2 marks
Two particles $A$ and $B$ , of masses $3$ kg and $5$ kg, are connected by a light inextensible string that passes over a smooth fixed pulley. The particles hang vertically with the string taut and are released from rest. Take $g=9.8$ m s⁻².
Find the magnitude and direction of the force exerted by the string on the pulley.2 marks
A particle $P$ of mass $4$ kg lies on a smooth horizontal table. It is connected by a light inextensible string, passing over a smooth pulley at the edge of the table, to a particle $Q$ of mass $6$ kg that hangs freely. The string is taut and $P$ is released from rest. Take $g=9.8$ m s⁻².
Find the acceleration of the particles.3 marks

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).