Two 1.50 kg balls are attached to the ends of a thin rod oi length 100 cm and ne

Question

Two 1.50 kg balls are attached to the ends of a thin rod oi length 100 cm and negligible mass. The rod is free to rotate in a vertical plane without friction about a horizontal axis through its center. With thr rod initially horizontal as shown to the left, a 100.0 g wad of wot putty drops onto one of the balls, hitting it with a speed of 10.00 m/s and thru sticking to it a) What is the angular speed of the system Just alter the putty wad hits? b) How far does the rod rotate before stopping and reversing?

Explanation / Answer

Part a)

Linear Momentum of putty = 0.1kg * 10 m/s =1
Angular momentum = linear momentum ÷ radius
L = 1 ÷ 0.05 m
L = 20

Angular momentum is conserved
Initially only the putty is moving, so only the putty has momentum
After collision, the putty, the rod, and the 2 masses have momentum

I total = mass * radius^2
I putty = 0.1 * 0.05^2
I 2 masses = 2 * 1.5 kg * 0.05m^2

I total =2 * 1.5 kg * 0.05m^2 + 0.1 * 0.05^2
I total = 0.3
Initial angular momentum = final angular momentum
20 = 0.3 *
= 66.67 radians/sec

Ans- Angular speed just after the putty wad hits is 66.67 radians/sec

Part b)

v=rxw

r=v/w

=10/66.67

=0.149 m

Ans- Rod will rotae 0.149 m

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