Department of Natural Sciences

Clayton College & State University

 

November 10, 2004

 

Physics 2211 – Quiz 9

 

 

Name  ____SOLUTION_________________________________

 

 

1. How much torque must be applied to the hoop having a moment of inertia about its central symmetry axis of 1.50 kg-m2 if it is to uniformly accelerate from rest to 10.0 rad/s in 10.0 s? 

 

St = I a

 

w = w0 +a t

 

a = (w - w0)/t

 

a = (10.0 rad/s- 0)/(10.0 s) = 1.00 rad/s2

 

St = (1.50 kg-m2) (1.00 rad/s2) = 1.50 Nm

 

2. Given A = 2i - 6j + 4k and B = 8j - 2k, find A x B.

 

A x B = | i        j       k  | = i (12 - 32) – j (-4) + k (16) = -20 i + 4 j = 16 k

             |2     -6        4  | 

             |0      8       -2  |