| Term | Definition |
|---|---|
when is work said to be done | When a force acting on a body displaces it in its own direction. |
formula for work | work = force * displacement |
what happens if force or displacement is 0 | then the resultant work will also be 0 |
how can work done be negative | if friction takes energy away, then it does negative work. |
SI unit of work | joule |
other unit | Nm |
1 kgfm | 9.8 joules |
energy | The capacity of a body to do work. When a body does work, it loses energy, but when work is done on a body, it gains energy. |
si unit | joule |
how can 1 joule of energy be defined | the amount of energy possessed by a body when 1 N is applied on it to move 1 m is joule. |
mechanical energy | the energy possessed by a body due to its position or motion. |
types of mechanical energy | kinetic and potential energy |
kinetic energy | The energy possessed by a body by virtue of its motion. |
what does kinetic energy depend on | the mass of the body, and the speed at which its moving |
formula of KE | 1/2 * mass * speed^2
[1/2mv^2] |
potential eneregy | the energy possessed by a body by virtue of its position or configuration. |
gravitational potential energy | energy stored by a body due to its height in a gravitational field. |
what does GPE depend on | the mass of the body, the height at which it is kept, and the acceleration due to gravity [ 9.8 m/s^2] |
formula | mass * acceleration due to gravity * height
[m*g*h] |
elastic potential energy | the energy possessed by a body in its deformed state when work is done to compress, deform, or stretch it |
how is a trampoline an example of EPE | when you jump on it, the shape changes and PE is stored in it. the released energy does work by making you jump higher. |
energy transformation | since energy can neither be created nor destroyed, it changes from one form to another. |
photosynthesis energy transformation [explained] | the light energy from the sun is converted to chemical energy through the process of photosynthesis. when we consume plants, this chemical energy is stored in our bodies as muscular energy. we use this muscular energy to do work, hence, it converts to mechanical energy. |
photosynthesis energy transformation | Light energy-> chemical energy-> muscular energy -> mechanical energy |
burning of fuel energy transformation [explanation] | The chemical energy of fuel is converted into heat energy in power plants. This heat is used to boil water. The steam moves the shaft of a turbine, and the energy becomes mechanical energy. With the help of the turbine, this is converted into electrical energy. |
burning of fuel energy transformation | chemical energy -> heat energy -> mechanical energy -> electrical energy |
explosion of atomic bombs energy transformation [explanation] | the atomic bomb give off enormous amounts of heat and light energy when exploded. |
atomic bomb explosion energy transformation | atomic energy -> heat energy & light energy |
car energy transformation [explanation] | The chemical energy of the fuel is converted to heat energy upon burning. The heat energy moves the piston and generates mechanical energy. The movement of the piston makes the car move, causing the mechanical energy to transform into kinetic energy. |
car energy transformation | chemical energy -> heat energy -> mechanical energy -> kinetic energy |
bow & arrow energy transformation [explanation] | to pull the string, we use muscular energy. when the string of pulled back, the energy is stored as elastic potential energy. when we let go of the string and the arrow flies, it gets converted to kinetic energy. |
bow & arrow energy transformation | muscular energy -> elastic potential energy -> kinetic energy |
riding a bike energy transformation [explanation] | to pedal, we use muscular energy. as the cycle moves, it gets converted to kinetic energy. due to friction, some of the kinetic energy gets converted to heat energy. |
examples of mechanical energy conversion | free-falling body, pendulum, rollercoaster, and hydroelectricity power plant. |
power | the amount of work done by a body in a unit time. |
formula | work energy
-------- or ------------
time time |
what does it depend on | the work done/ energy and time in seconds |
si unit | Watt |
other unit | joule/s |
1 horsepower | 746 watts |
define watt | 1 watt is said to be the power of a body if it is capable of doing a joule of work in 1 second |
difference between energy & power | energy can be converted from one form to another, unlike power.
energy can be stored, unlike power. |