Forces, Energy And Power Flashcards
(35 cards)
Describe the principle of conservation of energy.
The principle of conservation of energy states that energy cannot be created or destroyed, but can be transferred from one form to another, keeping the total energy in a closed system constant.
Define energy in the context of physics.
Energy is defined as the capacity to do work and comes in different forms such as gravitational potential energy, kinetic energy, internal energy, elastic potential energy, and electrical potential energy.
How does gravitational potential energy change with height?
Gravitational potential energy increases as an object’s height above the ground increases, depending on the object’s position in a gravitational field and its mass.
Explain kinetic energy and its dependence on mass and velocity.
Kinetic energy is the energy stored by an object when it is moving, and it is dependent on the object’s mass and velocity.
What is internal energy?
Internal energy is equal to the sum of all the kinetic energies and potential energies of all the particles of an object.
Describe elastic potential energy.
Elastic potential energy is the energy stored by an object when it is squashed or stretched.
What factors influence electrical potential energy?
Electrical potential energy is dependent on a charged object’s position in an electric field.
How is energy transferred when work is done?
Energy is transferred from one form to another when work is done, such as when kinetic energy is converted into elastic potential energy when an object is squashed.
Explain how energy is emitted or absorbed in the form of electromagnetic radiation.
Energy is emitted or absorbed in the form of electromagnetic radiation when thermal/internal energy is transmitted, for example, by infrared radiation from a radiator.
Describe the energy transformation that occurs when a ball is thrown into the air.
When a ball is thrown into the air, kinetic energy is converted into gravitational potential energy as it rises, and then back into kinetic energy as it falls.
What happens to kinetic energy when a ball works against resistive forces?
When a ball works against resistive forces, such as air resistance, the initial kinetic energy given to the ball is not equal to the maximum gravitational potential energy when the ball stops in mid-air, as some energy is transferred to the environment as heat.
Define work done in physics.
Work done (W) is defined as the force causing a motion multiplied by the distance travelled in the direction of the motion.
What is the formula for calculating work done?
The formula for calculating work done is W = F s cos θ, where F is the force, s is the distance, and θ is the angle between the force and the direction of motion.
Describe the relationship between work done and the change in volume of a gas at constant pressure.
Work done on a gas to change its volume at constant pressure can be calculated using the formula W = p ΔV, where p is the pressure and ΔV is the change in volume.
How is efficiency calculated in a system?
Efficiency is calculated by dividing the useful power output by the total energy input, expressed as a percentage by multiplying the result by 100.
Define kinetic energy and its formula.
Kinetic energy (E_k) is the energy of an object in motion, calculated using the formula E_k = 1/2 mv^2, where m is the mass and v is the velocity of the object.
Explain why the efficiency of a system is never 100%.
The efficiency of a system is never 100% because energy is always lost due to various forms of friction, such as kinetic energy being converted to internal and sound energy.
What factors contribute to energy loss in a system?
Energy loss in a system can occur due to friction, heat transfer, and the conversion of kinetic energy to internal and sound energy.
How can you derive the equation for kinetic energy from Newton’s 2nd law?
The equation for kinetic energy can be derived by considering an object of mass m that accelerates uniformly from rest to velocity v, using the relationships between force, mass, acceleration, and distance.
What does the variable ‘s’ represent in the context of work done?
In the context of work done, ‘s’ represents the distance travelled by the object.
What is the significance of the angle θ in the context of work done?
The angle θ represents the angle between the direction of the force applied and the direction of motion, affecting the calculation of work done.
How can efficiency be expressed as a percentage?
Efficiency can be expressed as a percentage by multiplying the ratio of useful power output to total energy input by 100.
Describe the difference between gravitational potential energy and elastic potential energy.
Gravitational potential energy depends on an object’s position in a gravitational field and its mass, while elastic potential energy depends on an object’s elasticity or spring constant and its change in length.
Explain the relationship between work done and gravitational potential energy.
If a force is applied to an object and it does positive work (increasing the object’s height), the gravitational potential energy of the object will increase. Conversely, if the height decreases, the gravitational potential energy will decrease.
