- #1
antoman
- 11
- 0
First of all I am sorry for my awful english.
Electric motor starts turning wheel with a constant power of P=25W and J=3 kg*m^2. With what angular velocity the wheel spins after 7s(from start), if the efficiency is 60%
P=M*ω
M=J*α
Ok so i have equation that gives correct number(solution) for this particular case, but i want to to know how did guy that wrote it came up with it and if its correct anyway.
so, equation is:
ω=sqrt((2*P*t)/J)=10,80 rad/s.
Correct answer is ω≈8.4 rad/s (100% correct its from our exam)
I tried to get to this equation by myself so i did this:
ω=P/M=P/(J*α)=P*t/(J*ω) so
ω^2=P*t/J
ω=sqrt(P*t/J)
The other thing that bothers me is that efficiency is not iven used. So any help how to develop correct equation would be nice.
Homework Statement
Electric motor starts turning wheel with a constant power of P=25W and J=3 kg*m^2. With what angular velocity the wheel spins after 7s(from start), if the efficiency is 60%
Homework Equations
P=M*ω
M=J*α
The Attempt at a Solution
Ok so i have equation that gives correct number(solution) for this particular case, but i want to to know how did guy that wrote it came up with it and if its correct anyway.
so, equation is:
ω=sqrt((2*P*t)/J)=10,80 rad/s.
Correct answer is ω≈8.4 rad/s (100% correct its from our exam)
I tried to get to this equation by myself so i did this:
ω=P/M=P/(J*α)=P*t/(J*ω) so
ω^2=P*t/J
ω=sqrt(P*t/J)
The other thing that bothers me is that efficiency is not iven used. So any help how to develop correct equation would be nice.