3.3 | work, energy, and power

what is work done in physics?

the energy transferred when a force moves an object through a distance in the direction of the force. if the force is at an angle, only the component of the force in the direction of movement is used.

what is the unit of work done?

joules

what is the principle of conservation of energy?

in a closed system, energy cannot be created or destroyed, only transferred from one form to another. the total energy before and after any transformation remains the same.

what is kinetic energy?

the energy of an object due to its motion, ek = 1/2mv²

what is the si unit of kinetic energy?

joules, or kgm²s⁻².

what is gravitational potential energy (gpe)?

the energy stored in an object due to its position in a gravitational field, ep = mgh.

what happens to energy when an object is lifted and then dropped?

when lifted, it gains gravitational potential energy; when dropped, that energy is converted to kinetic energy as it falls.

what is the relationship between kinetic and potential energy in a closed loop?

in the absence of external forces, energy exchanges between kinetic and potential forms, with total energy conserved: mgh = ½mv².

how does mass affect final speed in free fall?

mass has no effect on final speed in free fall because all objects experience the same gravitational acceleration.

what is power in physics?

the rate at which energy is transferred or work is done, calculated as p = w/t or p = fv

what is the unit of power?

watts, where 1 watt = 1 joule per second

how do you calculate power for an object moving at constant velocity?

if an object moves at constant velocity against resistive forces, power is calculated as p = fv, where f is the resistive force and v is the velocity.

what is efficiency in physics?

the ratio of useful output energy to total input energy, expressed as a percentage: efficiency = (useful output / total input) × 100.

why is some energy always 'lost' in real systems?

some energy is transferred to less useful forms, though total energy is still conserved.