Two people sit opposite each other on the edge of a rotating disk of radius, R, and negligible mass. One person has a mass of 40kg, the other of 50kg. The disk is rotating at 30 revs/min. What is the rotational kinetic energy if R=1.5m?

Rotational Kinetic Energy (KE) = (1/2) x Moment of Inertia (I) x (Angular Velocity (w) )2I=SUM(MR2) = 40 x (1.5)2 + 50 x (1.5)2 = 90 x (1.5)2 = 202.5 kgm2w= 30 revs / min = 30 x (2π/60) = π (rad/s)KE= 0.5 x 202.5 x π2 = 101.25 π2
KE= 999.297.... ~ 1000J

JS
Answered by Joe S. Physics tutor

1623 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

A coil is connected to an analogue centre zero ammeter. A magnet is dropped (North pole first) so that it falls vertically and completely through the coil. What would be observe on the ammeter?


What is the difference between linearly, directly and inversely proportional relationships?


Explain the photoelectric effect, when does it occur and what is its significance in understanding the nature of light ? (6)


If a bulb has a current of 20mA and voltage of 5V, and the current cost of electricity is £3 for a kW/hour. How much money would you spend to power the bulb for 8 hours? Are these good estimates for the current, voltage and cost of electricity?


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