# speed and velocity

• Oct 9th 2006, 02:07 AM
jacs
speed and velocity
A particle moves along a straight line so that its displacement x metres from a fixed point O is given by x = t^3 - 6t^2 + 9t + 5, where t is measured in seconds.

What is the average velocity of the particle over the first 3 seconds?

What is the average speed of the particle over the first 3 seconds?

I got the average speed to be 8/3 m's (which i hope is correct) but not sure what to do about the velocity.

thanks
• Oct 9th 2006, 03:12 AM
CaptainBlack
Quote:

Originally Posted by jacs
A particle moves along a straight line so that its displacement x metres from a fixed point O is given by x = t^3 - 6t^2 + 9t + 5, where t is measured in seconds.

What is the average velocity of the particle over the first 3 seconds?

What is the average speed of the particle over the first 3 seconds?

I got the average speed to be 8/3 m's (which i hope is correct) but not sure what to do about the velocity.

thanks

The average velocity between t_1 and t_2 is:

v_average = [x(t_2) - x(t_1)] / [t_2 - t_1]

You are given the expression for x in terms of t, so you should now be able
to find the average velocity.

RonL
• Oct 9th 2006, 05:54 AM
topsquark
Quote:

Originally Posted by jacs
A particle moves along a straight line so that its displacement x metres from a fixed point O is given by x = t^3 - 6t^2 + 9t + 5, where t is measured in seconds.

What is the average velocity of the particle over the first 3 seconds?

What is the average speed of the particle over the first 3 seconds?

I got the average speed to be 8/3 m's (which i hope is correct) but not sure what to do about the velocity.

thanks