Work Energy And Power Question 155
Question: A mass of 10 gm moving with a velocity of 100 cm/s strikes a pendulum bob of mass 10 gm. The two masses stick together. The maximum height reached by the system now is $ (g=10m/s^{2}) $ [MP PET 1993]
Options:
A) Zero
B) 5 cm
C) 2.5 cm
D) 1.25 cm
Show Answer
Answer:
Correct Answer: D
Solution:
Initially mass 10 gm moves with velocity 100 cm/s \
Initial momentum = 10 × 100 = $ 1000\frac{gm\times m}{\sec } $
After collision system moves with velocity $ {v _{sys\text{.}}} $
then Final momentum = $ (10+10)\times {v _{sys\text{.}}} $
By applying the conservation of momentum 10000 = $ 20\times {v _{sys\text{.}}} $
therefore $ {v _{sys\text{.}}}==50\ cm/s $
If system rises upto height h then $ h=\frac{v _{sys\text{.}}^{2}}{2g}=\frac{50\times 50}{2\times 1000}=\frac{2.5}{2}=1.25\ cm $
