WORK AND ENERGY
Frequently Asked Questions
Work is done when a force causes displacement of an object in the direction of the force.
Work done \((W) = Force (F) × Displacement (s) × cos\,\theta\), where \(\theta\) is the angle between force and direction of displacement.
The SI unit of work is joule (J).
A force must act on the object and the object must move in the direction of the force.
Energy is the capacity to do work or cause change.
The main forms are kinetic energy and potential energy; other forms include mechanical, chemical, electrical, heat, and nuclear energy.
Kinetic energy is the energy possessed by a body due to its motion.
Kinetic Energy \((KE) =\frac{1}{2} \times (\text{mass } m)\times (\text{velocity } v)^2\)
Potential energy is the stored energy an object has due to its position or configuration.
Gravitational Potential Energy (PE) = mass (m) × gravity (g) × height (h)
Mechanical energy is the sum of kinetic and potential energy in a system.
A moving car has kinetic energy.
Water at the top of a dam possesses potential energy.
Energy can neither be created nor destroyed; it only changes form. The total energy in a closed system remains constant.
In a pendulum, energy continuously converts between kinetic and potential, but total energy stays the same.
Power is the rate of doing work or transferring energy per unit time.
Power (P) = Work done (W) / Time taken (t); unit: watt (W)
The SI unit of power is watt (W).
Work is energy transferred by force; energy is the ability to do work; power is the rate of doing work.
One joule is the work done when a force of one newton displaces an object by one meter in the direction of force.
Elastic potential energy.
It is transformed into another form (e.g., heat, sound).
Kinetic energy.
Wattmeter.
Energy conversion is changing energy from one form to another, such as chemical energy to electrical energy.
Gravity determines the amount of gravitational potential energy based on an object's height.
Burning wood converts chemical energy to heat and light.
Work done is zero.
No, it possesses zero kinetic energy but may have potential energy.
Yes, via work, heat, light, electrical, etc.
Electric motor.
Some mechanical energy is converted to heat due to friction.
Power itself is scalar and non-negative, but work rate direction may be considered negative depending on context.
As chemical energy.
Energy is required for all actions: moving, eating, running devices, etc.
It converts water's potential energy to kinetic and then to electrical energy.
Work is energy transfer due to displacement by force; energy is the ability to perform work.
It stores chemical energy and converts it to electrical energy.
Energy flows from the sun to producers, then to consumers via food chain.
The rate at which the appliance consumes energy per unit time.
Lighting a bulb.
Potential energy converts to kinetic energy.
It guides efficient energy usage and device design.
No, according to the law of conservation of energy.
Light energy from the sun.
