A barbell consists of two identical masses, each of mas m, at the end of a massl
ID: 1788208 • Letter: A
Question
A barbell consists of two identical masses, each of mas m, at the end of a massless rod. We will treat the masses as point masses. The barbell is then rotated in a plane (in two dimensions ) about a point along the rod which is a distance L1 from one mass and L2 from the other. The barbell rotates at a constant angular velocity. Which of the following statements is correct?
a. The kinetic energy of the barbell is 0.5*m*(L12 + L22)*w2. The masses rotate at different linear speeds.
b. The kinetic energy of the barbell is 0.5*m*L2*w2, since the masses rotate at the same linear speed and L is the length of the barbell.
c. The kinetic energy of the barbell is 0.5*m*(L12 + L22)*w2. The masses rotate at the same linear speed, since they rotate together.
d. The kinetic energy of the barbell is 0.5*I*w2 , where I, the moment of inertia, is mL2. Here, L is the length of the rod.
Explanation / Answer
Option A is correct, the barbaad rotate with different linear speed because their location from the axis of rotation is different but their angular velocity is same.