Blake accelerates a sled carrying his little sister from rest. The sled and sister have a total mass m, the coefficient of kinetic friction between the sled and the ground is μk , and Blake causes the rope connected to the sled to have a constant tension force T that makes an angle θ with the horizontal. Any frictional forces between the sled and the snow are negligible.

The period of a pendulum varies directly as the square root of the length of the pendulum and inversely as the square root of the acceleration due to gravity. find the period when the length is 144 cm and the acceleration due to gravity is 980 cm per second squared, if the period is 7pi seconds when the length is 289 cm and the acceleration due to gravity is 980 cm per second squared.