# Physics,Question ,Solved but about Units?

posted by
**Katherine** on
.

These are “plug-in-the-number” tasks to familiarize you with the

main formulas that link the physics concepts of this chapter. They

are one-step substitutions, much less challenging than the Think

and Solve problems that follow.

Average speed !

total distance covered

travel time

34. Show that the average speed of a rabbit that runs a distance

of 30 m in a time of 2 s is 15 m/s.

35. Calculate your average walking speed when you step

1.0 m in 0.5 s.

Acceleration !

change of velocity

time interval

!

"v

"t

Here is the example practice question but Im not sure how to work it out,perhaps this is more specific?

Physics - Steve, Wednesday, October 10, 2012 at 2:25pm

keep in mind that if there is very little data provided, the formulas involved will be relatively simple.

Always keep track of the units. That way you will know whether you are manipulating the various quantities correctly.

#34.

speed is distance/time. so, since you are given a distance and a time,

speed = 30m/2s = 30/2 m/s = 15m/s

#35.

1.0m/0.5s = 1/.5 m/s = 2m/s

as for acceleration, just as speed is change in distance over elapsed time, acceleration is change in speed over elapsed time.

So, if a runner increases his speed from 10m/s to 20m/s in 2 seconds, the acceleration a is

a = (20-10)m/s / 2s = 10/2 m/s^2 = 5m/s^2

How do I keep track of the Units?