Module 3: Chapter 5 - Work, Energy, and Power Flashcards
What is the equation for mechanical power?
P=FV
Power = Force x Velocity
How is P=FV derived?
P = W/t
P = Fd/t
P = F(d/t)
P=FV
What are the 10 energy stores?
- Thermal
- Kinetic
- Nuclear
- Elastic Potential
- Gravitational Potential
- Chemical Potential
- Magnetic
- Electrostatic
- Radiant
- Sound
What are the 4 Energy transfer pathways?
- Heating
- Radiation (light, nuclear, sound)
- Electrical Work
- Mechanical Work
When is work done?
Work is done when a force acts on an object causing it to move
What is the equation for work done?
Work done = force x distance (in the direction that the force is applied)
W=Fs cosθ
What is energy?
Energy is the ability/capacity to do work
What is the work done by a force perpendicular to the direction of motion?
0 J
How do you calculate the work done when the force applied is at an angle to the direction of motion?
Resolve the force in the direction of motion and then use W=Fd
What is the equation for impulse?
Ft = m(v-u)
What does the area under a force distance graph represent?
The work done
Calculate the work done
40J
Is work done whenever a force is applied to an object?
No, Work is only done when the force applied causes the object to move
A force of 1x10^4 N acts vertically upwards on a lift, causing it to accelerate from rest, at 2ms^-2 for 5s. Calulate the power after 1s and the average power needed over the 5s
a) 2x10^4 W
b) 5x10^4 W
A car of weight 1.5x10^4 N drives up a slope at a steady speed of 12ms^-1. The car gains 1m of height for every 10m travelled in the horizontal direction. Calculat the power of the engine.
17911 W
A skeir of mass 60kg descends a slope at an angle of 30° to the horizontal. The skier passes a point P at 10ms^-1. At 100m further down the slope, at point Q, they are travelling at 20 ms^-1. Calculate the average resistive force acting on the skier between points P and Q
204.3N
Draw a graph for the kinetic energy and the gravitation potential energy of a bouncing ball
What is the law of conservation of energy?
Within a closed system the total amount of energy is constant, energy cannot be created or destroyed, only transferred between one store and another
What is energy efficiency?
A measure of how much useful energy you get out of an object from the total energy you put into it
What is the equation for energy efficiency?
Efficiency = [(useful energy output) / (total energy input)] x 100
What is a sankey diagram?
A diagram showing useful (going across) and wasted (going down) energy
Calculated the wasted power in the form of heat
1560.2W
What is the equation for electrical energy transferred?
E = ItV
What happens to wasted energy?
It is dissipated to the surroundings in the form of heat/light/sound
On a fair ground ride, the track descends by a vertical drop of 100m over a distance of 150m along a track. A train of mass 2500kg on the track reaches a speed of 40ms^-1 at the bottom of the descent, after beign at rest on the top. Calculate the resistive force it had to overcome
difficult question
2510N
What is power?
The rate of transfer of energy
The rate of doing work
What is motive power?
the output power of an engine
What is the equation for power?
Power = work done / time
What is the equation for kinetic energy?
Ek = 0.5mv²
How is the equation for kinetic energy derived?
What is the work energy principle?
If a constant force acts on an object over a certain distance, the work done by the force is equal to the gain in the kinetic energy of the object
What is gravitational potential energy?
The energy of an object within a gravitation field by virtue of its position
What is kinetic energy?
The energy a body with mass posses by virtue of its motion
What is chemical energy?
Energy contained within the chemical bonds between atoms - it can be released through a chemical reaction
What is elastic potential energy?
Energy stored in an object as a result of a reversible change in its shape
What is electrostatic energy?
Energy of electrical charges due to their position in an electric field
What is nuclear energy?
Energy within the nuclei of atoms - it can be released through nuclear reactions
What is radiant energy?
Energy associated with all electromagnetic waves, stored within the oscillating electric and magnetic fields
What is sound energy?
Energy of a mechanical wave due to the movement of atoms
What is thermal energy?
The sum of the random potential and kinetic energies of atoms in a system
What is the equation for kinetic energy in terms of momentum?
Ek = p² / 2m
Kinetic energy = momentum² / 2(mass)
