find average velocity

Question

A rock is dropped. Find its average velocity from t = 3 seconds to t = 5 seconds. (Enter feet/sec)

Answer 1

Brenda, use the distance formula, to start with, in which is:

 

d(t)=1/2*g*t^2

 

g=-32 feet/sec^2

 

d(3)=1/2*(-32)*3^2=-144 feet

d(5)=1/2*(-32)*5^2=-400 feet

 

The average velocity is taking the slope between the two points in which is:

 

v_ave=(-400--144)/(5-3)=(-400+144)/2=-128 feet/sec Note: The negative sign indicates the rock is going down.