Rotational Motion Question 95
Question: A disc of radius 2 m and mass 100 kg rolls on a horizontal floor. Its centre of mass has speed of 20 cm/s. How much work is needed to stop it?
Options:
A) 2 J
B) 1 J
C) 3 J
D) 30 kJ
Show Answer
Answer:
Correct Answer: C
Solution:
-
[c] $ w=\frac{1}{2}mV^{2}( 1+\frac{K^{2}}{r^{2}} ) $
$ =\frac{1}{2}\times 100{{(20\times {10^{-2}})}^{2}}( 1+\frac{1}{2} ) $
$ =\frac{4}{3}\times \frac{3}{2}=3J $
