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What is energy?

What is energy?. Energy measures the ability for things to change themselves or to cause change in other things. A joule (J) is the S.I. unit of measurement for energy. Pushing a 1-kilogram object with a force of one newton for a distance of one meter uses one joule of energy.

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What is energy?

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  1. What is energy? • Energy measures the ability for things to change themselves or to cause change in other things. • A joule (J) is the S.I. unit of measurement for energy. Pushing a 1-kilogram object with a force of one newton for a distance of one meter uses one joule of energy

  2. 1. Kinetic Energy An object that moves has kinetic energy (when you walk, run, jump -- you have K.E.) How much Kinetic Energy an object has depends on 2 things: a. The mass of the object b. The speed its moving at The more speed an object has the more KE it has. Ex: a fastball has more KE than a slow curve ball. The more massan object has the more KE it has. Ex: Think of a tennis ball rolling across your foot …compared to a bowling ball rolling across your foot

  3. The formula used to find kinetic energy is: Ek = mass x velocity (speed)2 2 ** Notice the velocity (speed) is squared. This means if you go twice as fast, your energy increases by four times (22=4) SAMPLE PROBLEM: Find the kinetic energy of a 50 kg swimmer, swimming at a speed of 4 m/sec. (Use 5 steps to solve) YES -- 5 STEPS!! 1. Ek = mass x speed 2 2 2. Ek = 50 kg x (4m/sec) 2 ÷ 2 3. Ek= 50kg x 16 m2/sec2÷2 4. Ek = 800kg/m2/sec2 ÷2 5. Ek = 400 joules

  4. 2. Potential Energy - is "stored" energy or energy an object has due to its position. • Ex: An archer gives potential energy to a • bow by pulling it back. The stored energy can be • used to send the arrow flying through the air. • Potential energy associated with objects that can be stretched (bow) or compressed (spring) is called elastic potential energy. • Potential energy that depends on height is called gravitational potential energy. • Ex: A person standing on the edge of • an 3-meter cliff.

  5. The formula for finding gravitational potential energy (when the mass is in kilograms) is: Ep= mass x acceleration due to gravity x height SAMPLE PROBLEM: Find the potential energy of a 50 kg diver on a 15 meter cliff. Ep = mass x acceleration due to gravity x height Ep = 50 kg x 9.8 m/sec2 x 15 meters Ep = 7350 joules When the mass (weight) is given in newtons you would use the formula Ep = mass x height

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