The position of a 2.75 *10^5 N training helicopter under test is given by

r = (0.020 m/s^3)(t^3)i + (2.2 m/s)(t)j - (0.060 m/s^2)(t^2) k

Find the net force on the helicopter at t =5.0s.
Express your answer in terms of i,j,k. Express your coefficient using two significant figures.

2 answers

just plug in 5 for t:

r = (0.020 m/s^3)(5^3)i + (2.2 m/s)(5)j - (0.060 m/s^2)(5^2) k
1. take the second derivative of r to find acceleration.

2. then divide 2.75 *10^5 N by 9.8m/s^2 to find how much the helicopter weighs in kg

3. multiply your result from 1 with your result from 2