Question

The motor in an electric saw brings the circular blade from rest up to the rated angular velocity of 80.0 rev/s in 240.0 rev. One type of blade has a moment of inertia of 1.41x10-3 kgm2. What constant net torque must the motor apply to the blade?

a. 0.150 Nm
b. 0.250 Nm
c. 0.350 Nm
d. 0.450 Nm

Answer 1

The constant net torque the motor must apply to the blade is 0.00047 Nm.

Step-by-step explanation:

To find the torque required to bring the circular blade up to the rated angular velocity, we can use the formula:

Torque = Moment of inertia x Angular acceleration

Since the blade starts from rest and reaches an angular velocity of 80.0 rev/s in 240.0 rev, we can calculate the angular acceleration:

Angular acceleration = Change in angular velocity / Change in time

Angular acceleration = (80.0 rev/s - 0 rev/s) / (240.0 rev) = 0.333 rev/s²

Now we can substitute the values into the formula:

Torque = (1.41x10^-3 kgm²)(0.333 rev/s²) = 4.70x10^-4 Nm

Therefore, the constant net torque the motor must apply to the blade is 0.00047 Nm.