Question

A small body of mass 'm' is attached to one end of a light inelastic string of length l. The other end of the string is fixed. The string is held initially taut and horizontal and then body is released. The centripetal acceleration of the body and the tension in the string when the string reaches vertical position will be –

• A. g, mg
• B. 2g, 3 mg
• C. 3g, 2mg
• D. 3g, 3 mg

Answer 1

Answer: (B)

2g, 3 mg

Answer 2

Loss in P.E. = gain in K.E.

mg r = $\frac{1}{2}$ mv² ̃ v² = 2g

ra_c = $\frac{v^{2}}{r}$ = 2g

T – mg cos q = $\frac{mv^{2}}{r}$

T = 3 mg