Help with Dynamics FE Examination Problem (Forces and Motion)?
A 550 Kg mass initially at rest is acted upon by a force of 50e^t N. What are the acceleration , velocity and displacement of the mass at t=4s?
A 550 Kg mass initially at rest is acted upon by a force of 50e^t N. What are the acceleration , velocity and displacement of the mass at t=4s?
az_lender
Favorite Answer
Apparently we are to assume that "t" is in seconds,
though they SHOULD say so!
a = (50 e^t N)/(550 kg)
v = integral from 0 to t of (50 e^u) du/(550 kg)
= v0 + (50 e^t-50)/(550 kg)
= (e^t - 1)(N*s)/(11 kg)
x = integral from 0 to t of (e^u - 1) du/(11 kg)
= x0 + (e^t - t - 1)/(11 kg)
a(4s) = (50*54.6 m/s^2)/550 = 4.96 m/s^2
v(4s) = (e^4 -1)(m/s)/11 = 4.87 m/s
x(4s) = (e^4 - 4 - 1) m/11 = 4.51 m