JEE MAIN - Physics (2021 - 25th July Morning Shift - No. 25)
A pendulum bob has a speed of 3 m/s at its lowest position. The pendulum is 50 cm long. The speed of bob, when the length makes an angle of 60$$^\circ$$ to the vertical will be (g = 10 m/s2) ____________ m/s.
Answer
2
Explanation
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Applying work energy theorem :
wg + wT = $$\Delta$$K
$$-$$mgl(1 $$-$$ cos60$$^\circ$$) = $${1 \over 2}$$mv2 $$-$$ $${1 \over 2}$$mu2
v2 = u2 $$-$$ 2gl(1 $$-$$ cos60$$^\circ$$)
v2 = 9 $$-$$ 2 $$\times$$ 10 $$\times$$ 0.5$$\left( {{1 \over 2}} \right)$$
v2 = 4
v = 2 m/s
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