# Revolutions of and Electric Drill

1. Nov 5, 2008

### uno

1. A variable speed electric drill motor turning at 100 rev/s is uniformly accelerated at 53.0 rev/s2 up to 210 rev/s. How many turns does it make in the process?

2. (Accel f - Accel) i x speed

3. I took 210 - 53 = 157 and multiplied that by 100 and that gave me 15,700 rev. This anser is incorrect. Please advise.

2. Nov 5, 2008

### joeyar

Data we have: Initial angular velocity, acceleration, final angular velocity. We want angular displacement.

This problem is the rotational analogue of one we would use the for the equation Vf^2 = Vi^2 + 2ax.

Replace V with angular velocity, a with acceleration and solve for x. Since we are working in units of rev, no division by 2*pi will be necessary - the answer your calculator gives you will be the answer you want.

3. Nov 5, 2008

### uno

I got it! Thanks so much for your help.