# Homework Help: Angular velocity

1. Aug 22, 2008

### clokey34

1. The problem statement, all variables and given/known data

The following data are for the angular displacement of the knee in cycling
measured in degrees. Using radian measure, compute the angular velocity
and acceleration when the knee angle is 119.1 degrees. The sampling
frequency was 50 Hz. What is a problem you may encounter when calculating
higher derivatives from sampled displacement data?
98.0, 103.5, 109.0, 114.2, 119.1, 123.4, 126.9

2. Relevant equations

Angular velocity is degrees per unit time.

3. The attempt at a solution

I only have the angle. And a frequency but not a discrete time variable? Thanks!

2. Aug 22, 2008

### Hootenanny

Staff Emeritus
What is the definition of frequency?

3. Aug 23, 2008

### clokey34

Yeah I agree it is 50 cycles a second but then I'm not sure how to apply that?

4. Aug 23, 2008

### Hootenanny

Staff Emeritus
So, you know that every second there are fifty measurements taken. Equally, you know that each measurement is separated by $1/50 = 0.02$ seconds.

Can you go from here?

5. Aug 25, 2008

### clokey34

Oh right you make it so simple! Thanks.

So change in velocity over change in time. Change in time is 0.02sec

change before
119.1 -114.2 = 4.9deg
4.9/0.02=245deg

change after
123.4 - 119.1 = 4.3deg
4.3/0.02=215deg

(245+215)/2= 230deg.sec-1

Accel= change of rate of velocity is (230-245)/2
=-1500ms-2