A stone tied to the end of a string, 80 cm long, is whirled in a horizontal circle with a constant speed. If the stone makes 14 revolutions in 25 seconds what is the magnitude and direction of the acceleration of the stone?

Answer 1

80cm=0.8m
T=25/14=1.786...seconds
v=(2pi*r)/T=2pi(0.8)/1.786...=2.815...m/s
a=v^2/r=2.815...^2/0.8=9.904m/s^2, towards the centre along the radius vector of the circle

Answer 2

9.9