Can’t be created can’t be destroyed Energy Can’t be created can’t be destroyed

Forms of Energy Kinetic Energy and Work Potential Energy Mechanical Electrical Thermal Sound Light Mechanical Gravitational Energy Elastic Energy Chemical Energy Nuclear Energy

Kinetic Energy and Work Kinetic Energy - the kinetic energy of an object is the energy that it possesses due to its motion. 𝐾𝐸 = 1 2 𝑚𝑣² KE – Kinetic Energy (J) m – mass (kg) v – velocity (m/s) Unit is Joule (J)

Kinetic Energy Practice Problems The flash has a mass of 88 kg and is said to be able to run at the speed of light. If he were to go for a light jog at the speed of sound 340 m/s. What would be his kinetic Energy? When Iron Man is fully suited up he has a mass of 191 kg. When he is travelling at his max velocity of 1700 m/s what would be his kinetic energy?

Kinetic Energy

Kinetic Energy and Work Work - When a force acts upon an object to cause a displacement of the object, it is said that work was done upon the object. 𝑊 = 𝐹𝑑 W - Work(J) F – Force (N) d – displacement (m) Unit is Joule (J)

Work Practice Problems Ant-man has the ability to lift 500 kg. Find the force required to lift such a weight and the work done if the weight is lifted 2 m. Rumor has it that Chuck Norris has the strength to lift 100 tons, so accelerating a 1,250,000 kg train at 0.25 m/s² 4 m should be no problem. Find the work that would be done.

Work

Kinetic Energy and Work Efficiency is calculated by dividing the output work by input work. This number will always be less than one. We multiply that number by 100 to get the percentage. Machines are almost always less than 100% efficient, mostly due to friction. %𝐸= 𝑊 𝑜𝑢𝑡 𝑥 100 𝑊 𝑖𝑛

Kinetic Energy and Work Efficiency Practice Problems. A man pushes a box with 500 N of force up a 1.5 m ramp. It requires 1000 J of energy to push the box up the ramp. Find the %E. A man pushes the same box with 150 N of force down a 1.5 m ramp. It requires 300 J of energy to push the box down the ramp. Find the %E.

Kinetic Energy and Work In the last two practice problem the work in was greater than the work out. However, the law of conservation of energy states energy cannot be created or destroyed. How is energy conserved, where is the extra energy going?

Kinetic Energy and Work Heat or Thermal Energy - is simply the transfer of energy from a hot object to a colder object until the object reaches equilibrium. Heat is transferred by: Conduction Convection Radiation

Kinetic Energy and Work Electric Energy – is the motion of electrons as they travel through a circuit and do work. 𝐸 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐 =𝑃𝑡 E – Electric Energy (J) P – Power (W) t – Time (s) The average US house uses 10,932 kWh, or 3.9x10¹º J a year, which requires 1,344.6 kg (2964.3 lbs) of coal.

Kinetic Energy and Work Sound Energy – When a force causes an object to vibrate, the energy is transferred through a medium as a wave. 𝑓 = 1 𝑇 f – frequency (Hz) T – period (s)

Kinetic Energy and Work Light or Electromagnetic energy - a form of energy that is reflected or emitted from objects in the form of electrical and magnetic waves that can travel through space.

Potential Energy Potential Energy – the stored energy of an object due to the position possessed by the object.

Potential Energy Gravitational Potential Energy – the energy stored in an object as the result of its vertical position or height. 𝑃𝐸=𝑚𝑔ℎ PE – Grav. Pot. Energy (J) m – mass (kg) h – vertical height (m)

Gravitational Potential Energy Practice Problems Find the gravitational potential of the basketball if the basketball has a mass of 0.625 kg.

Gravitational Potential Energy Practice Problems Find the gravitational potential of the man if he has a mass of 90 kg.

Potential Energy Elastic Potential Energy – the energy stored in elastic materials as the result of their stretching or compressing. 𝑃𝐸 𝐸𝑙𝑎𝑠𝑡𝑖𝑐 = 1 2 𝑘 𝑥 2 PE – Elastic Pot. Energy (J) k – spring constant (N/m) x- the distance the spring has been compressed or stretched from equilibrium(m)

Elastic Potential Energy Practice Problems A spring with a spring constant of 10 N/m is compressed 0.2 m. Find the elastic potential energy.

Elastic Potential Energy Practice Problems 2. An archer pulls her bowstring back 0.4 m. The bow has a spring constant of 1150 N/m. Find the elastic potential energy.

Potential Energy Chemical Energy – is energy stored in the bonds of chemical compounds. 1 cal = 4.186 J Example: Apple – 65 cal = 272 J 12 oz Dr. P – 150 cal = 628 J AA Alkaline battery – 9360 J

Potential Energy Nuclear Energy – is the energy in the nucleus, or core, of an atom. 𝐸=𝑚 𝑐 2 E – Energy (J) m – mass (kg) c – speed of light 3 x 10⁸ m/s

Nuclear Fusion Nuclear Fission Potential Energy  nuclear reaction in which two or more atomic nuclei join to form a new nucleus. a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts.

Mechanical Energy Mechanical Energy –The sum of kinetic and potential energy in a closed system. 𝑀𝐸 = 𝐾𝐸 + 𝑃𝐸 ME – Mechanical Energy (J) KE – Kinetic Energy (J) PE – Potential Energy (J)

Mechanical Energy Practice Problems What is the Mechanical energy at point A? What is the Mechanical energy at Point B? What is the Mechanical energy at Point C if m = 100 kg, v = 5.5 m/s, and h = 1.5 m? B 3000 J C A 3000 J

The Law of Conservation of Energy "Energy can neither be created nor destroyed“ Energy is transformed from on type of energy to another type of energy. Gravitation Potential Energy is transferred to Kinetic energy and back into Gravitational Potential Energy.

Identify the Different Energies Transfers Example From To Battery Food Wind Turbine TNT Sun Space Heater

Law of Conservation of Energy Practice Problems We found the gravitation potential energy of a basketball when suspended 126.5 m above the ground. Using the law of conservation of energy calculate the velocity the ball would have right before it hit the ground.

Law of Conservation of Energy Practice Problems 2. A pendulum with a mass of 0.25 kg swings back and forth. It reaches a max velocity of 10 m/s. Calculate the max height the pendulum will reach.

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