Plssssss help, sorry for the trouble

Question

A 62.8 kg bicyclist on a 10.0 kg bicycle speeds up from 3.1 to 18.7. How much work was done to increase the kinetic energy of the bicyclist?

Answer 1

Concentrate on the formula for Kinetic Energy (also known as Work), which is 0.5 Times Mass Times The Square Of Velocity and written as KE = 0.5mv².

At 3.1 Meters Per Second, the cyclist-bicycle system is already in an active energy (or "working") state of 

[0.5×72.8×3.1²] kilogram•meter²/second².

The cyclist then forces greater power (which is work done divided by time taken) into the pedals to raise his speed to 18.7 Meters Per Second. The cyclist-bicycle system is then taken to an active energy state of [0.5×72.8×18.7²] kilogram•meter²/second².

Next build the expression:

0.5[(62.8 + 10) Kilograms]{18.7 Meters Per Second}² Minus

0.5[(62.8 + 10) Kilograms]{3.1 Meters Per Second}².

This last reduces to [0.5×72.8×18.7²] − [0.5×72.8×3.1²] or

12378.912 Kilogram-Dot-Meter-Squared-Per-Second-Squared.

The kilogram•meter²/second² constitutes the unit of Work (or Kinetic Energy) in

Physics known as the Joule.