Calculation of torque to stop a wheel.

• cheapstrike
In summary, the problem involves finding the torque required to stop a wheel with a moment of inertia of 5×10-3kg-m2, rotating at a frequency of 20 rev/s, in a time of 10s. The options for the answer are (A) 2π×10-2Nm, (B) 2π×102Nm, (C) 4π×10-2Nm, and (D) 4π×102Nm, with the correct answer being (A). The solution involves using the rotational kinematic equations and the relation between torque and angular acceleration to find the change in rotational kinetic energy and the power delivered. The final answer is 10-2πN.m.
cheapstrike

Homework Statement

A wheel of moment of inertia 5×10-3kg-m2 is making 20 rev/s. Find the torque required to stop it in 10s is

(A) 2π×10-2Nm (B) 2π×102Nm

(C) 4π×10-2Nm (D) 4π×102Nm

Homework Equations

ω=2πƒ (ƒ=frequency)
Power (P) = Γω.
P = W/t.
W = ΔK.E. = (1/2)Iω2.

The Attempt at a Solution

The power delivered is equal to the rate of doing work which is equal to the change in rotational kinetic energy.
On calculating, I get the final answer as 10-2πN.m. Kindly help.

You are thinking in a very complicated way! Keep it simple! Use the rotational kinematic equations and the relation between torque and angular acceleration.

Show your working. Note that the power isn't constant. Power = torque * angular velocity
And the angular velocity is reducing.

PS My internet connection is currently unreliable so sorry in advance if I "dissapear".

CWatters said:
Show your working. Note that the power isn't constant. Power = torque * angular velocity
And the angular velocity is reducing.

PS My internet connection is currently unreliable so sorry in advance if I "dissapear".
Oh yes. The angular velocity isn't constant. I didn't pay attention to that. Thanks.

Mastermind01 said:
You are thinking in a very complicated way! Keep it simple! Use the rotational kinematic equations and the relation between torque and angular acceleration.
Yeah! Turns out this was a simple question. Thanks a lot!

What is torque?

Torque is a measure of rotational force that causes an object to rotate around an axis. It is typically measured in units of Newton-meters (N*m) or foot-pounds (ft*lb).

How is torque related to stopping a wheel?

When a wheel is spinning, it has rotational kinetic energy. In order to stop the wheel, an opposing torque must be applied to counteract this energy and bring the wheel to a halt.

What factors affect the amount of torque required to stop a wheel?

The amount of torque required to stop a wheel depends on the mass of the wheel, the speed at which it is spinning, and the amount of friction between the wheel and its axle or bearings.

How can torque be calculated to stop a wheel?

The formula for calculating torque to stop a wheel is: torque (T) = moment of inertia (I) * angular deceleration (α). The moment of inertia can be calculated using the mass and dimensions of the wheel, while the angular deceleration can be determined from the change in angular velocity over time.

What are some practical applications of calculating torque to stop a wheel?

Knowing the required torque to stop a wheel can be useful in designing braking systems for vehicles or machinery, as well as in determining the amount of force needed to manually stop a spinning object.

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