1.4 Energy concepts Flashcards
What is work?
When a force causes a body to move, work is done by the force on the body. Work is equal to the energy that is transferred (to the body) as a result of the force and is the product of the magnitude of the force and the distance moved in the direction of the force
What is the equation for work?
W=Fx
Where F is the force in N, x is the distance travelled in the direction of the force in m and W is the work, measured in J.
What is the equation for work in a direction?
W=Fxcosθ
What is kinetic energy and its equation?
A body can have kinetic energy due to its motion and potential energy.
The kinetic energy of a body can be calculated using the following equation:
E=1/2 mv^2
Where m is the mass of the body in kg, v is the velocity in m s-1 and E is the energy in J.
What is gravitational potential energy and its equation?
Gravitational potential energy is the energy possessed by an object by virtue of its position. The change in gravitational potential energy can be calculated using this equation:
∆E=mg∆h
Where m is the mass of the body in kg, g is the acceleration due to gravity at sea level = 9.81 m s-2, Δh is the change in height in m and ΔE is the change in energy in J.
What is elastic potential energy and its equation?
Elastic potential energy is the energy possessed by an object when it has been deformed due to forces acting on it, such as a compressed spring or a stretched rubber band. It is calculated using this equation:
E=1/2 kx^2
Where k is the spring constant in N m-1, x is the extension in m and E is the energy in J.
What is the principle of conservation of energy?
The principle of conservation of energy states that energy cannot be created or destroyed, only transferred from one form to another.
This means that the total energy of a system will remain constant even if the type of energy changes.
For example, a ball thrown vertically will initially have kinetic energy; however, as it rises it will lose kinetic energy and gain gravitational potential energy. Assuming there are no dissipative or resistive forces, the loss in kinetic energy will be equal to the gain in gravitational potential energy.
What is the equation related to kinetic energy and work done?
fx = 1/2mv^2 - 1/2mu^2
What is power defined as?
Power is defined as the rate of energy transfer. It is the amount of energy that is transferred per second and is measured in W where 1 W = 1 J s-1.
What is the equation for power?
P = W/t = ∆E/t
Where P is the power in W, W is the work done in J, t is the time in s and ΔE is the change in energy in J.
What is the equation for efficiency?
%efficiency = useful energy / total energy x100
