Q 55

A ball of mass m is attached to a thin string and whirled in a vertical circle or radius r. The tension in the string at point e where the ball is moving with speed v is
A) mg
B) mg - mv^{2}/r
C) mg + mv^{2}/r
D) mv^{2}/r
E) none of the above.

Q 57

An L-shaped piece, represented by the shaded area on the figure, is cut from a metal plate of uniform thickness. The point that corresponds to the center of mass of the L-shaped piece is
A) 1
B) 2
C) 3
D) 4
E) 5

Q 58

The shaded area in the figure represents a uniformly thick sheet of metal. The center of mass of the sheet is closest to point
A) 1
B) 2
C) 3
D) 4
E) 5