Section 2 Energy Conversions Energy conversion is a

Section 2: Energy Conversions • Energy conversion is a change from one form of energy into another

Section 2: Energy Conversions From Kinetic to Potential and Back Trampoline Example: • Kinetic energy when you jump • Gravitational Potential Energy when you change your position (with respect to the ground) and jump • Potential energy when the trampoline stretches

Section 2: Energy Conversions Self Check: At what point does a roller coaster have the greatest potential energy? The greatest kinetic energy? A roller coaster has the greatest potential energy at the top of the highest hill (usually the first hill), and the greatest kinetic energy at the bottom of the highest hill.

Section 2: Energy Conversions Involving Chemical Energy Chemical energy of food is converted into kinetic energy when you are active and thermal energy to maintain body temperature Do we only get energy from eating plants? (Hint: Energy pyramid) Because an animal eats the grass before we eat the animal, we still receive chemical energy but only 10% of the energy that the animal received from the grass.

Let’s Review • What is energy conversion? An energy conversion is a change from one form of energy to another. Any form of energy can be converted into any other form of energy

Let’s Review • Describe an example in which electrical energy is converted into thermal energy. In an iron, as an example, electrical energy is converted into thermal energy.

Let’s Review • Describe an energy conversion involving chemical energy. When a natural gas stove is lit, the chemical energy in the natural gas is converted into thermal energy.

Let’s Review • Describe the kinetic-potential energy conversions that occur when you bounce a basketball.

Let’s Review When you bounce a basketball, you give it kinetic energy. At the moment the ball hits the ground, its kinetic energy is greatest and its potential energy is zero. At that moment, the change in the shape that occurs when it hits the ground gives the ball potential energy that is used when the ball moves back upward. When the ball bounces back up toward your hand , its kinetic energy is converted into potential energy because the position changes. At the moment the ball is at the top of its bounce, its kinetic energy is zero.

Energy and Machines • You transfer energy to the nutcracker and it transfers energy to the walnut P 226 The nutcracker will not transfer more energy to the walnut than you transfer to the nutcracker

Energy and Machines • Machines are energy converters • When machines transfer energy, energy conversions can often result

Why energy conversions are important They make energy useful by converting energy to a form of energy we can use Energy efficiency is a comparison to the amount of energy before a conversion with the amount of useful energy after a conversion…efficiency means less waste Work input is always greater than work output

• Bouncing ball

Baseball hitting a bat

Energy and Work