Question

A 0.5 kg pendulum bob is raised to 1.0 m above the floor, as shown in the image to the right. The bob is then released from rest. When the bob is 0.8 m above the floor, its speed is most nearly…

(A) 5 m/s

(B) 4 m/s

(C) 2 m/s

(D) 1 m/s

Answer 1

$mgH=mgh+mv^2/2\to$

$v=\sqrt{2g(H-h)}= \sqrt{2\cdot9.81\cdot (1-0.8)}=1.98\ (m/s)\approx2\ (m/s)$

$(C)\ 2\ m/s$ . Answer