Force problem?

Question

The position of a 2.75 x 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).

Find the net force on the helocopter at t = 5.0 sec.

Express the vector F in the form Fx, Fy, Fz.

Answer 1

Looks like the weight of the helicopter is 2.75 x 10^5 N, so the mass is 27.5/9.8 x 10^4 kg.

r = 0.02 t^3 i + 2.2 t j - 0.06 t k
v = dr/dt = 0.06 t^2 i + 2.2 j - 0.6 k
a = dv/dt = 0.12 t i

F = ma = 27.5/9.8 x 10^4 x 0.12 x 5 N
= 1.68 x 10^4 i N

Fx = 1.68 x 10^4 N
Fy = Fz = 0

Answer 2

du u know diffrentiation

f=m*a

here a can b written as dv/dt and vas dx/dt

hence f can b written as m* d^2(x)/(dt)^2

now diffrentiate the above equation which u have given and find the answer