Conversion of Energy Forms of Energy Work Energy

Conversion of Energy Forms of Energy Work Energy

Work • The product of force and distance moved in the direction of the force • W=Fxd • Units: Newton-meter, Nm – Equivalent to Joule, J

Work Example • A force of 10 N is applied to a box to move it 2 m along the floor. What is the work done on the box? • A bodybuilder, 1. 6 m tall lifted a 30 -kg mass from the ground up to his head. How much work did he do?

Which force does more work?

Energy • The ability to do work • Work ~ Energy • Units: Nm, J • May be: – Transferred – Stored – Transformed

Forms of Energy • Kinetic Energy – Energy due to motion – Equation: • EK = ½ mv 2 • Potential Energy – Energy due to position – Equation: • EP = mgh

Examples • What is the kinetic energy of a 3 -kilogram ball that is rolling at 2 meters per second? • What is the potential energy of a 3 kilogram-ball that is 3 m above the ground?

Forms of Energy • Chemical Energy – Energy due to chemical reaction • Nuclear Energy – Energy due to nuclear reaction

Forms of Energy • Thermal Energy – Energy transferred due to difference in temperature • Electrical Energy – Energy due to movement of charges

Forms of Energy • Light Energy • Sound Energy

Conversion of Energy

Conversion of Energy Is this right or wrong?

Conversion of Energy

Example 1 • A box of mass 3 kg is dropped from a height of 5 m. Neglecting air resistance, calculate: – The potential energy of the box before it is dropped – The kinetic energy of the box just before it reaches the ground – The speed of the box just before it strikes the ground

Example 2 • A ball of mass 60 g is thrown upwards with an initial speed of 30 m/s. If air resistance is negligible, calculate: – The initial kinetic energy of the ball – The initial potential energy of the ball – The potential energy of the ball when it reaches its greatest height – The greatest height reached by the ball