How work works.
What is work
Work is a fundamental concept in physics, and it can be defined as the transfer of energy from one object to another by the application of force. Work is done when an external force causes an object to move or change its shape. The amount of work done on an object depends on the magnitude of the force applied and the distance over which it acts. For example, if you lift a box up two meters with a force of 10 Newtons (N), then you have done 20 joules (J) of work – 10 N multiplied by 2 m.
Work can be positive, negative or zero. If an object is moved in the same direction as the applied force, the work is positive. If the object is moved in the opposite direction to the applied force, the work is negative. And if the object does not move, zero work has been done – if you push against a wall for a long time , you might use a lot of energy but unless you manage to move the wall you have done zero work.
Work-energy theorem
The work-energy theorem states that the total work done by the forces on an object is equal to the change in its kinetic energy. This means that when a force acts upon an object, it does work and increases or decreases its kinetic energy accordingly.
This relationship between work and energy can be used to calculate how much power is required for certain tasks. Power is defined as the rate at which work is done, usually expressed in watts (W). To calculate power, divide the amount of work done by time taken; for instance, if you lifted a box up two meters with a force of 10 N over five seconds, then your power output would be 4 W (20 J divided by 5 s). The higher the power output, the faster an object will move or accelerate given enough time. In fact, one watt is equivalent to one joule per second.
Kinetic energy
Kinetic energy is the energy of motion, and it can be found in any object that is moving. It is calculated by multiplying half an object’s mass with its velocity squared (KE = ½mv²). Kinetic energy increases as an object moves faster, so a car travelling at 100 km/h has more kinetic energy than one travelling at 50 km/h.
The relationship between work and kinetic energy can be seen when a force acts upon an object to cause it to move or accelerate; this force does work on the object which increases its kinetic energy accordingly. For example, when you push a box across the floor, your pushing force does work on the box which causes it to move and increase its kinetic energy.
Kinetic energy can also be found in everyday objects such as leaves falling from trees or rockets blasting off into space. The amount of kinetic energy possessed by each depends on their mass and speed. For instance, a rocket blasting off will have much greater amounts than a leaf floating down from a tree due to its higher speed.
Potential energy
Potential energy is the stored energy of an object due to its position, configuration, electrical charge and other factors. It can be released and converted into kinetic energy when a force such as gravity acts upon it. Potential energy is related to work in that it requires work to move an object from one potential state to another; for example, lifting a heavy box up onto a shelf requires work which increases the box’s potential energy.
Gravitational potential energy is the amount of stored energy an object has due to its height above Earth’s surface – the higher up it is, the more gravitational potential energy it has.
Elastic potential energy refers to objects that are stretched or compressed beyond their natural shape and have built-up tension ready for release; rubber bands and springs are examples of this type of potential energy.
Chemical potential energies come from chemical bonds between atoms in molecules; these bonds store large amounts of latent heat which can be released through combustion reactions like burning wood or gasoline.
Conservation of energy
The law of conservation of energy states that the total amount of energy in a closed system remains constant. This means that potential and kinetic energies can be converted from one form to another, but the total amount will always remain the same.
For example, when a ball is thrown into the air it gains gravitational potential energy as it rises, while it slows down and its kinetic energy decreases. When it reaches its highest point and begins to fall back down again, its gravitational potential energy is converted into kinetic energy until it hits the ground.
This law has far-reaching implications for physics: all forms of motion are governed by this principle – from planets orbiting stars to electrons moving around atoms. In addition to explaining physical phenomena on Earth and beyond our atmosphere, this law also helps us understand everyday occurrences like roller coasters at amusement parks – these rides use stored mechanical potential energies which are then released through gravity and friction during their descent down hills and loops!
Work done by a constant force
Work done by a steady, unchanging (constant) force, is straightforward to calculate. This type of work can be calculated using the equation W = Fd, where F is the magnitude of the applied force and d is displacement.
For example, if a person pushes a box with 10 Newtons (N) of force for 2 meters (m), then they have done 20 Joules (J) worth of work on that box.
The concept of work done by a constant force also applies to the rotational motion, such as when turning a wheel or cranking an engine. In this case, torque – which is equal to force multiplied by distance from pivot point – replaces force in our equation: W = τθ, where τ represents torque and θ represents angular displacement in radians.
For instance, if you apply 5 Nm (Newton-meters) worth of torque to turn a wheel through 1.5708 radians (equivalent to 90 degrees) then you have done 450 J worth of work on it!
Work done by a variable force
Work done by a variable force is more complex than work done by a constant force, as the magnitude of the applied force changes over time. This means that equations such as W = Fd and W = τθ are not applicable in this case, since they assume that the applied force remains constant throughout. To calculate work done by a variable force, we must use integration – an advanced mathematical technique which involves summing up all of the small changes in energy over time to get an overall result.
Integration allows us to take into account any changes in velocity or acceleration during motion, making it possible to accurately calculate work done even when forces vary with time. For example, if you were pushing a box across a room at varying speeds then integration would allow you to determine how much total energy was transferred from your body to the box during its journey. Similarly, if you were turning a wheel at different rates then integration could be used to find out how much total torque was applied over its rotation angle. Integration is thus essential for calculating work done by variable forces and understanding their effects on objects!
Power
Power is the rate at which work is done, and can be calculated by dividing the amount of work done by the time taken to do it. Power is usually expressed in watts (W), with one watt being equal to one joule per second. A light bulb typically uses around 60 W of power, while a lightning bolt can have up to 10 billion W!
The power output of an object or system depends on its efficiency – how much of its energy input it converts into useful output. The most efficient systems are those that convert all their input energy into useful output: a 100% efficient engine would convert all fuel used into motion. However, no real-world system has perfect efficiency; even the best engines only achieve around 40-50%. Some energy will always be lost as heat or sound during operation.
Power also depends on factors such as friction and air resistance which reduce an object’s speed over time and thus decrease its overall power output. To counteract these effects engineers must design machines with low drag coefficients and high torque outputs in order to maximize their efficiency and performance.
Mechanical energy
Mechanical energy is the combination of potential and kinetic energy.
Potential energy is stored in an object due to its position or configuration, while kinetic energy is the energy of motion. When these two energies are combined they create mechanical energy, which can be used to do work.
For example, when a roller coaster car climbs up a hill it gains potential energy as it rises higher above the ground; this potential energy then converts into kinetic energy as it descends down the other side and accelerates towards its final destination.
The sum of these two energies makes up the mechanical energy and the mechanical power that propels the car along its track. The amount of mechanical power available depends on how much potential and kinetic energies are present in a system at any given time; for instance if there is more potential than kinetic energy then acceleration will be slower.
Thermal energy and temperature
Thermal energy is the energy of random motion of particles. Temperature is a measure of how much thermal energy an object contains; as temperature increases, so does the average kinetic energy of its particles. Heat is the transfer of thermal energy from one object to another due to a difference in their temperatures.
This process occurs when two objects with different temperatures come into contact with each other until they reach equilibrium – that is, until both objects have the same temperature.
Heat can be converted into work using a heat engine:; when fuel combusts in an engine it releases heat which then causes pistons to move and generate mechanical power.
Work can also be converted into heat – Consider how rubbing your hands together quickly creates friction which generates heat and warms them up! Work can be completely converted into heat but heat can only be partially converted into work.
