Question

You are given that the “heart shaped object” in Fig. 4 has a moment of inertia I = 0.5kgm2. Use this to calculate

10NI - 15 N 3700 100 6 am I 4 cm 3 an 160300 SN

the change in angular momentum L of the object in 4s. Hint: L⃗ = ⃗τ∆t.

(b) This question deals with angular momentum conservation. Two boys of mass 100 kg each stand at the center of a rotating merry-go-round (MGR) in the shape of a disk of radius 1 m and mass 10 kg. The platform rotates at ω = 0.40 rad/s. Let’s call this configuration instant A.

(i) Determine the angular momentum of the system (two boy + MGR) at instant A. Hint: You will need to find the moment of inertia of the disk and the two boys (point masses).

(ii) Now the boys start walking radially towards the rim. When one of them has reached the rim, the other is three-quarters of the way there - let’s call this instant B. Argue that angular momentum is conserved during the process of the boys walking to the rim, i.e. between instants A and B.

(iii) Use angular momentum conservation to find the angular velocity of the system at instant B.

(iv) Calulate the kinetic energy of the system at instant B. Hint: The system only has rotational kinetic energy.