So time and time again my professor has reinforced that speed and velocity are not the same. One is a scalar the other a vector, ect... But time and time again I will be asked to solve homework problems that ask for the speed of an object, yet the answer is velocity and using equations for velocity. Let me give you an example:(adsbygoogle = window.adsbygoogle || []).push({});

A truck covers 37.0 m in 8.90 s while smoothly slowing down to final speed of 2.70 m/s.

(a) Find its original speed.

Answer: using the average Velocity equation 1/2(Vi + Vf) and the fact that the average VELOCITY is 37.0m/8.90s, we can solve the equation for initial VELOCITY! and get Vi = 5.7m/s.

Now this does not make sense to me, first of all, if we are looking for initial speed why do we use average velocity equation. Second, if they are the same in this case, which is what I think might be happening, how do you know? The problem does not state the direction of motion in anyway. when do you then know that average velocity is the same as average speed? I just dont understand this, and I try to be very strict on the words that I see being used in the problem. When I see speed, I think one thing(distance over time) and velocity another(displacement over time). Can anyone clear this issue up for me?

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# Homework Help: Speed and Velocity(Driving Me Crazy)

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