Question

A 5.00 kg toolbox is suspended from the end of a virtually mass-less vertical string. A time-dependent upward force is applied to the upper portion of the string, and the toolbox moves upward with a velocity magnitude that varies such that: v(t) = (.800 m/s^3)t^2 + (4.00 m/s^2)t

Part 1: How long does it take to reach a velocity of 15 m/s

Part 2: What is the Tension in the string when the object has a velocity of 15m/s? For this problem do not assume that the force of gravity on the toolbox has already been taken into account by the equation. (Hint: you must find the acceleration at the time you found in Part 1. But don't forget to add in the force of gravity on the toolbox also)

Answer 1