Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.

Trending News

Promoted
Vegeta
Lv 4
Vegeta asked in Science & MathematicsEngineering · 8 years ago

Torque question?? 10 pts!!?

Suppose an electric motor exerts a constant torque of 15 N.m on a grindstone (solid disc) mounted on its shaft

Mass of grindstone = 64 kg

Radius of grindstone = 0.25 m

System starts from rest.

Find

a) work done by motor in 8 seconds

b) the average power of the motor

Thanks!!!

Update:

Well this is a previous exam question.... its not impossible to do given the information..

2 Answers

Relevance
  • Ecko
    Lv 7
    8 years ago
    Favorite Answer

    Work out the moment of inertia from the shape and mass and radius.

    I = (m x r^2) / 2

    Calculate the speed and so power

    omega = angular velocity_radians = (2 x pi x RPM) / 60

    delta_t = Moment_of_Inertia x delta_omega / Torque

    (This would be 4 seconds for the average power)

    Power_W = torque_N.m x omega

    Calculate the work as change in energy_joules = average_power * total_time

    This is really an integral but just use the average power at 4 seconds as this is all linear..

  • kasab
    Lv 7
    8 years ago

    The speed of the motor is missing. More torque has to be exerted at the start condition for the angular acceleration.

Still have questions? Get your answers by asking now.