Calculate kinetic and potential energy

Find kinetic energy with ½mv² and gravitational potential energy with mgh.

Kinetic energy is the energy of motion: KE = ½ × m × v². Mass is in kilograms and speed in metres per second, so the answer is in joules.

A 1500 kg car at 20 m/s has KE = 0.5 × 1500 × 20² = 300,000 J. Gravitational potential energy is PE = m × g × h. A 2 kg object lifted 10 m, with g = 9.81, has PE = 196.2 J.

Classic Graphing 84 · Kinetic energy

Start on the main screen: Press 2nd then mode (QUIT) to get back to the home screen. Pressing clear on a menu also backs out of it.

Type 1 ÷ 2 × 1500 × 20², using the x² key. The speed is squared before it is multiplied.
1÷2×1500×20x²
Press enter.
enter

You should see1/2*1500*20² 300000

Classic Graphing 84 key reference

Classic Graphing 84 · Potential energy

Start on the main screen: Press 2nd then mode (QUIT) to get back to the home screen. Pressing clear on a menu also backs out of it.

Type m × g × h as 2 × 9.81 × 10 and press enter.
2×9.81×10enter

You should see196.2

Classic Graphing 84 key reference

Natural Scientific 991

Start on the main screen: Press MENU, then 1 (Calculate) to return to the main calculation screen. AC clears the line you are on.

Type 1 ÷ 2 × 1500 × 20² and press = .
1÷2×1500×20x²=

You should see300000

Natural Scientific 991 key reference

RPN Scientific 15

Start on the main screen: There is no menu to leave. Press the back arrow to clear a number you are typing, or CLx (g then back arrow) to clear the X register.

Square the speed first: 20, then g and x² (the √x key).
20gx²√x
Key in the mass and press ×, then key in 2 and press ÷ for the half.
1500×2÷

You should see300,000.0000

RPN Scientific 15 key reference

Tips

Doubling the speed makes the kinetic energy four times bigger, because of the square.
Keep every number in base units (kg, m, s) or the joules will not come out right.