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
!
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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?
Keeping track of units is important in physics because it helps ensure that your calculations are correct and that your final answer has the correct unit. Here are some guidelines to help you keep track of units:
1. Write down the given quantities with their units. For example, if you are given a distance of 30 meters, write it as 30 m.
2. Write down the formula you will be using and make sure the units for each term in the formula are consistent. If the units don't match, you may need to convert them to a common unit.
3. Perform the calculations, making sure to carry the units along. For example, if you are dividing a distance by a time, keep the units in the division as well. This will give you the correct unit for the final answer.
4. Cancel out units when possible. For example, if you are multiplying a distance by a time, the unit for distance (meters) and the unit for time (seconds) will cancel out, leaving you with the correct unit for speed (meters per second).
5. Check the unit of your final answer to make sure it is the expected unit. If not, double-check your calculations and conversions to find any errors.
By following these guidelines, you can ensure that you keep track of units and have accurate results in your physics calculations.