Presentation on theme: "Work. Energy. Power. Physical work Work (W) is defined as the force (F) times the distance (s) moved in the direction of the force (cos Θ ) NB! Θ is angle."— Presentation transcript:
Physical work Work (W) is defined as the force (F) times the distance (s) moved in the direction of the force (cos Θ ) NB! Θ is angle between the applied force and tirection of motion If there are no movement in the direction of force, then no work is done Work is scalar quantity Work is measured in joules (1J = 1Nm=1kgm 2 s -2 )
Work vs Energy Work done is equal to converted energy When work is done, energy is converted to different types. Kinetic energy (E k or KE) is the energy a body because it is moving Potential energy (E p or PE) is the energy stored in a body or in a system due to its position in a force field or due to its configuration – Gravitational potential energy is the energy a body has because of its position in vertical height relative to a given point (height from surface of earth)
Kinetic energy m – mass of body v – velocity (speed) of body Kinetic energy is scalar quantity measured in joules (1J)
Gravitational potential energy m – mass of body g=9.81 ms -2 – gravitational acceleration Δh – change in height (vertical) Potential energy is scalar quantity measured in joules (1J)
Conservation of energy Energy cannot be created or destroyed; only changed form one form to another There are many different forms of energy: – kinetic energy; – potential energy; – elastic potential energy; – heat energy; – light energy; – sound energy; – chemical energy; – electrical energy; – magnetic energy; – nuclear energy; – etc
Power Power (P) is measure how fast work (W) is done or how quickly energy is converted (ΔE): Δ t – is time taken in seconds Power is scalar quantity measured in watts (1W=1Js -1 =1kgm 2 s -3 )
Efficiency Efficiency is a ratio of how much work, energy or power we get out of a system compared to how much is put in Efficiency is scalar quantity and has no unit! It is measured usually in percentages.