A 10m long uniform beam is pivoted in its centre. A 30kg point mass is placed on one end of the beam. Where must a 50kg mass be placed in order to balance the beam?

For this question, we will use moments. A moment is defined as:Moment = force x perpendicular distance from pivotHere, the moment of the 30kg mass which acts anti-clockwise through the pivot. The moment is:M30kg = 30g x 5mThe force is 30g as F=ma with g being the acceleration under gravity. The perpendicular distance is 5m as the beam is pivoted in the centre and the mass is placed at the end of the beam.The moment of the 50kg mass is:M50kg = 50g x DWhere D is the distance from the pivot. Since we know for the beam to be balanced, the clockwise moment must be equal to the anti-clockwise moment, we can say:M30kg = M50kg30g x 5 = 50g x DWe can cancel out the g factor as it is present on both sides of the equation.30 x 5 = 50 x DD = (30 x 5)/50 = (30 x 1)/5 = 3mSo the mass must be placed 3m from the pivot which is also 8m from the end which the 30kg mass is placed on.

Answered by Joseph M. Physics tutor

2586 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

What is the maximum frequency photon of one of the photons produced when a electron and positron annihilate each other?


Using Fermat's Principle explain why it makes sense for light be refracted when crossing from one medium into another that has a different refractive index.


What would happen to n and Emax when  a) the intensity is reduced to 1/2 I but the wavelength λ is unchanged? b) the wavelength λ is reduced but the intensity is unchanged?


A small ball of mass 150 g is placed at a height of 20cm above the ground on an incline of 35°. It is released and allowed to roll down the slope; what will be the ball's speed when it reaches the ground? Assume friction and air resistance can be ignored.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences