A student spins a 1.2kg rock around above her head horizontally in an experiment which aims to model how satellites orbit the earth. The student counts 3 orbits per second when the string produces an orbit radius of 35cm.

Question

A student spins a 1.2kg rock around above her head horizontally in an experiment which aims to model how satellites orbit the earth. The student counts 3 orbits per second when the string produces an orbit radius of 35cm.
(a) Calculate the centripetal force acting on the rock.
(b) Describe the effects of two real forces acting on the revolving rock in this situation.

Damon · Answer

Fc = m v^2/r
circumference = C = 2 pi r = 2 pi * .35
speed = v = circumference/time = 2 pi *35/(1/3) meters/second
so
Fc = 1.2 * (6pi*.35)^2/.35 N

other force is gravity down
1.2*9.8 N
tan angle down from horizontal = 1.2*9.8 /Fc