How do I do this question?

To solve this you need to be familiar with the equations you have been given. Often it is difficult to know which equation or equations you need just by reading the problem. So, let’s approach this problem in an organized way so that we will not have to work so hard.

Go and get a sheet of paper and divide it into three columns. Really, if you do this you will be amazed at how easy word problems become.

In the first column put the information from the problem including the information regarding the unknown quantity. For this problem your first column might look like this from top to bottom: vi = 8.0m/s; d = 5.0m; vf = 6.2m/s; a = ?m/s^2.

Study the first column carefully and see if you can find an equation that has initial and final velocity, distance and acceleration. If you look carefully you should find this equation: vf^2 = vi^2 + 2ad. Put this equation in the middle column. Now we have to apply our algebra skills and solve this equation for ‘a’. You should get a = (vf^2 – vi^2) / 2d. This should be in the middle column too.

Now we move over to the third column and do the math. All we have to do is put the numbers and units from the first column into the equation from the middle column. Your third column might look like this from top to bottom: a = (6.2m/s)^2 – (8.0m/s)^2 / 2(5m); a = 38.44m^2 / s^2 – 64m^2 / s^2 / 10m; a = -25.56m^2 / s^2 / 10m; a = 2.56m/s^2.

Isn’t that nice? Each column has its own purpose and function. You can clearly and easily see exactly what you are doing and if you make a mistake it is easy to spot.

Average speed over the rough patch is 7.1 m/s ((8.0 + 6.2)/2).

Time on rough patch is 5.0m / 7.1m/s = .704 seconds

Acceleration = change in V / time = (6.2-8.0)/.704 = 2.56 m/s^2