Physics Flashcards
What is useful & wasted energy?
Useful energy: energy that actually performs task
Wasted energy: energy that converts to an unusable form
ie: a lightbulb produces useful light & wasted heat
What does the first law of thermodynamics state? What does the second law of thermodynamics state?
First law of thermodynamics: energy cannot be created or destroyed, but can be tranformed from 1 form to another
Second law of thermodynamics: no process can be 100% efficient, some energy will always remain in the form of thermal energy
List the types of energy transformations
Heat, light, sound, electrical, chemical, mechanical
What is potential energy? List its forms
Potential energy: stored energy
Elastic: work done to distort the object to give potential energy, once returned to original shape energy is released
Chemical: energy stored in bonds of chemical compounds, can be released during a chemical reaction
Nuclear: energy stored in an atom’s nucleus, nuclear chain reaction can release nuclear energy
Gravitational: energy of an object due to position above Earth’s surface (distance from ground), must be calculated using the height above a reference point.
Acceleration due to gravity - acceleration with which all objects near the Earth’s surface would fall if air friction was non-existent.
Amount of gravitational potential energy an object has = amount of work required to lift it
Force that gravity exerts is equal to its weight
calculated by Ep = mgh (Ep - gravitational potential energy, m - mass in kg, g - gravity on Earth is 9.81 m/s2 , h- height in m)
Why does mass ≠ weight?
Mass - quantity of matter in object, always stays the same
Weight - force of gravity on mass, changes depending on where you are in the universe
What is kinetic energy? What is it dependent on?
Kinetic energy: energy of motion, dependent on speed and mass of object
- When you do work on an object you are transferring your kinetic energy to the object
- In many transformations, not all of the work goes into Ek, some of it is always lost as heat
- Work done on an object causing it to move faster, kinetic energy increases
- Work done on an object causing it to move slower, kinetic energy decreases (called negative work)
If all work converts into Ek, (ignoring friction) then W= Ek then w= mv2 ÷ 2
If two objects fall from the same height but have different masses, which will travel at a faster rate, the lighter one or the heavier one? Which one would have more kinetic energy?
They will both travel at the same rate, as speed is not affected by the weight of the object. However, the heavier one will have more kinetic energy.
What is work?
Work - transfer of mechanical energy from 1 object to another, ability to do work, can be determined graphically
In order to move an object & give it kinetic energy, you have to put energy into it
w = f x d
(w - work in joules [J], f - force in netwons [N], distance in metres [m])
Highlight the difference between vectors and scalars (and provide examples)
Vectors:
- magnitude (number) and direction
- written with arrows
ie: displacement, velocity, acceleration, position
Scalars:
- magnitude (only provide a number)
ie: temperature, distance, speed (v)
Compare and contrast velocity and speed
Velocity: displacement travelled over a period of time, measures in m/s or km/h
Speed: distance travelled over time
FORMULA: v = d ÷ t
Compare and contrast displacement and distance
Displacement: straight line between two points, must have a direction (ie. N,E,S,W, +, -)
Distance: length of path actually taken
What is acceleration
Acceleration - a change in velocity over time, measured in m/s2
- Acceleration* - increase in speed
- Negative acceleration* - decrease in speed
FORMULA: a = [final velocity - inital velocity] ÷ time
Describe acceleration in a graph (object at rest then acceleration, constant positive acceleration, no acceleration)
a) Positive acceleration, object is at rest then accelerates
b) Constant positive acceleration
c) Constant or no acceleration, no change in velocity
What kind of movement does this graph illustrate?
Negative acceleration; object slows down
What kind of acceleration does this graph illustrate?
Positive acceleration, object is at rest then accelerates
What does this graph illustrate about velocity and acceleration?
Constant velocity, no acceleration, uniform acceleration
What does this graph illustrate about velocity and acceleration?
Constant negative velocity (velocity is decreasing), constant negative acceleration
What does this graph illustrate about velocity and acceleration?
Constant positive velocity, constant positive acceleration
