Additional Science: Physics (II) Flashcards
What is the equation for working out speed?
What is the equation for working out acceleration?
What is the equation for working out weight?
What is the equation for working out force?
What is the equation for working out work done?
What is the equation for working out momentum?
What do the parts of the distance-time graph tell you about movement?
a-b = moving
b-c = stopped
c-d = moving quicker (than at a-b as line is steeper)
What do the parts of the velocity-time graph tell you about movement?
a-b = accelerating quickly
b-c = steady speed
c-d = decelerating
d-e = stopped (steady speed)
e-f = accelerating quickly
f-g = steady speed
g-h = decelerating
How can you work out the distance traveled from a velocity-time graph?
Work out the area beneath the graph
When are the forces of an object balanced?
When it is still or travelling at a steady speed
What do unbalanced forces do to the movement of an object?
It will cause the object to speed up / slow down
What is the force of gravity on Earth?
10N/kg (9.8N/kg)
What is the equation for working out power?
Power (P) = work done (or energy transferred) (E) ÷ time take (s)
What is the equation for working out gravitational potential energy?
Gravitational potential energy (Ep) = mass (kg) x gravity (N/kg) x height (m)
How is work done to an elastic object stored?
Via elastic potential energy (shape is changed)
What is Hooke’s law?
Extension of an elastic object is directly proportional to force
Force (N) = spring constant (k) x extension (m)
F = k x e
How would you draw out an example of Hooke’s law in practice?
What happens to extension of an object if the force becomes too great?
The directly proportional extension of the object in relation to the force stops…
When stopping a car what can affect the thinking time?
Drugs and alcohol
Distractions
Tiredness
When stopping a car what can affect the breaking distance?
Speed
Mass of vehicle
Tyres
Brakes
Road surface
Weather
Why do falling objects reach terminal velocity?
The weight remains constant with gravity causing the object to accelerate
Air resistance is small to begin with, but as the object speeds up it increases
Eventually the air resistance will equal the weight (as this does not change)
Once the forces are balanced there can be no change in speed – terminal velocity
What is resultant force and when is the resultant force on an object zero?
The overall force in one direction – this is zero when the object is stationary
What can be described as a fluid?
What happens to the frictional forces as an object accelerates through a solid
Gases and liquids
Frictional forces increase as the speed increases, but eventually reach terminal velocity
What is momentum and what affects it?
Momentum is how quickly each kg of the object is moving – objects with great momentum are harder to stop
Momentum is affected by mass and velocity
What is the equation for working out kinetic energy?
Kinetic energy (J) = ½ mass (kg) x speed2 (m/s)
Ek = ½ mv2
Friction usually causes what type of energy to be lost?
Heat (thermal) energy
All objects with elastic potential energy are all able to do what?
Return to their original shape
During a collision or explosion between objects, what happens to the momentum?
The momentum in a collision or explosion is conserved
What safety features do you find in cars to help reduce the affect of momentum during a crash?
Cars are designed to convert kinetic energy safely in a crash via: -
Seatbelts
Crumple zones
Air bags
Side impact bars
In a car crash safety features are designed to what?
Increase the time taken to slow the passenger(s) down
How are static charges produced?
Rubbing an object to remove electrons (negative charges)
Objects which gain electrons become negatively charged
Objects which lose electrons become positively charged
When objects collect a static charge, which type of charge moves?
Negative charges only (the electrons can be moved, but the protons are held in the nucleus (not moving))
How does a photocopier use static charges?
Drum of the photocopier has positive charge
When light falls onto the drum it loses its charge – light shines through white bits, so only the black bits of the paper to copy remain charged
Ink is negatively charged so it is attracted to the positive parts of the drum
This is transferred to the paper
How does a smoke precipitator use static charges?
Dust and ash pass through a negatively charged grid and pick up a negative charge
Dust is then attracted to positively charged plates which are shaken and removed at intervals
How can spray-painting use static?
Paint is positively charged – these paint particles repel each other to create a fine mist
Objects being sprayed are negatively charged so the paint is attracted to it
When can static electricity be dangerous?
Static can be dangerous when flammable gases / liquids are used which a spark could ignite
E.g. petrol stations or operating theatres
How can the dangers of static electricity be reduced?
The dangers can be reduced by ‘earthing’ objects to prevent sparks from forming
What happens when 2 like charges are put together?
What happens when 2 opposite charges are put together?
Like charges repel
Opposite charges attract
What is an earth cable and what is it used for?
Earth cables must be good conductors (e.g. copper) to provide the electrons with an easy route to the ground
Why can a build-up in static charges cause a spark?
If the charge on an isolated object is great enough there may be a large enough potential difference between the object and the ground to spark (electrons jump the gap)
What are the symbols for the following: -
Switch
Cell
Battery
What are the symbols for the following: -
LDR
Diode
Resistor
What are the symbols for the following: -
Fuse
Lamp
Variable resistor
What are the symbols for the following: -
Voltmeter
Ammeter
Thermistor