A pendulum consists of a 2.0kg bob attached to a light 3.0m long string. While hanging at rest with the string vertical, the bob is struck a sharp horizontal blow, giving it a horizontal velocity of 4.5m/s. At the instant the spring makes an angle of 30degrees with the vertical. What is: a) the speed b)gravitational potential energy(relative to its value is at the the lowest point) c)the tension on the string d)what is the angle of the string with the vertical when the bob reaches its greatest height The work from the tension of the string is 0 because it is perpendicular to the displacement of the bob. Ki = 0 since it starts out at rest The conservation of energy is: Ui + Ki = Uf + Kf mgh + 0 = 0 1/2 m Vf^2 vf = root of 2gh Is this correct approach to answer part A? For Part B b)gravitational potential energy(relative to its value is at the the lowest point) Im not sure what to do. Is this the potential energy of the bob? c)the tension on the string Isn't the tension just MG? d) d)what is the angle of the string with the vertical when the bob reaches its greatest height Any hints on how to start this one?