A ball having a mass of 500 grams is dropped from a height of 9.00 meters. What is its kinetic energy when it hits the ground? Please explain what the answer is and how you got it. thank you!

Uk = 44.145 J

Explanation:

To calculate the kinetic energie (Uk), you can make use of this formula:

Uk = m * g * h

given m = 0.500 kg g = 9.81 m/ s² and height is 9.00 m

Substituting in the formula gives:

Uk = 0.500 * 9.81 * 9.00

Uk = 44.145 J

Extra:

Now let's examine the formula in relation to the SI units. If you understand the following, it will give you great insight in how smart Phisics is inter twained by looking at formulas and their standard units. It will save you time in future to convert formulas, if you use the right standard units.

The formula for kinetic energie is:

Uk = m * g * h

given m in kg g in m/ s² and h in m.

From the formula, you see that the unit of Uk must be kg * m/s² * m which is kg* m²/s² and since Uk is normally given in J, these both forms must be the same !

The main unit for Uk is the Joule. Now please see the picture, which shows the relation between the J and other SI units. Please understand that you can construct your 'own' formulas based these units. Now here is the time saver:

Because almost always the right units are given in a question, or because sometimes you can look up a constant in a table with an exotic and seemingly complicated unit, but that says a lot about the formula which must have been some how involved!

By this, I hope you now understand the implication of using the right standard SI units and how that can help you figure out what formula is needed.

current flows in a wire