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
Related Physics A Level answers
All answers ▸What are quarks?
An ideal gas undergoes a transformation in which both its pressure and volume double. How many times does the root mean square speed of the gas molecules increase?
Derive an expression for the time taken, (t) for a test mass to fall to the ground from a height (h) in a uniform gravitational field (g = 9.81 ms^-2)
The Σ0 baryon, composed of the quark combination uds, is produced through the strong interaction between a π+ meson and a neutron. π+ + n →Σ0 + X What is the quark composition of X?