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Kinetic and Potential Energy

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Presentation on theme: "Kinetic and Potential Energy"— Presentation transcript:

1 Kinetic and Potential Energy
- Energy can be described as the ability to produce heat or do work and can be broadly classified into two categories: Kinetic – related to an object’s motion Potential – related to an object’s stored energy - In a closed system, energy is always conserved and transferred from one form to another

2 Kinetic and Potential Energy
PE = mgh Potential Energy = mass × gravity × height (this gives us gravitational potential energy, GPE) Gravity = 9.8 m/s2 KE = ½ mv2  amount of work (force over a distance) needed to accelerate an object from rest to a speed of v Kinetic Energy = ½ × mass × velocity2

3 A 60 kg cheetah sits in a tree 5 m above ground. What is its GPE?
GPE = m × g × h = 60 kg × 9.8 m/s2 × 5 m = 2940 J

4 An iPhone is thrown up into the air and reaches a height of 5 m
An iPhone is thrown up into the air and reaches a height of 5 m. What is its GPE if the phone weighs 1.37 N? GPE = m × g × h = 1.37 N × 5 m = 6.85 J

5 Kinetic and Potential Energy
The relationship between kinetic and potential energy is: Total Energy = Kinetic Energy + Potential Energy

6 Relationship b/w Energy and Work
Since kinetic energy is energy of motion kinetic energy of an object = work needed to create observed motion As such, W = ΔKE Or W = ½ mv22 – ½ mv12

7 Relationship b/w Energy and Work
Since potential energy is stored energy potential energy of an object = work stored As such, W = mgh (because F × d)

8 PE and KE Practice 1. A ball has a mass of 0.3 kg. If the ball is above the ground at a height of 2.0 m, what is its gravitational potential energy? 2. The ball falls and halfway down to the ground, it is traveling at 4.43 m/s. What is the kinetic energy of the ball at that moment? 3. What will the speed of the ball be just before it hits the ground?


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