Forces and Motion Flashcards
Nano (metre)
x 10 *-9
Micro (metre)
x 10 *-6
Milli (metre)
x 10 *-3
Hecto (pascal)
x 10 *2
kilo (pascal)
x 10 *3
mega (metre)
x 10 *6
Giga (metre)
x 10 *9
In equations, charge is represented by … and measured in …
Q
Coulombs (C)
Acetate always
Gives away electrons and
is always positive
ACETATE IS GREAT
Polythene always
Takes electrons and
is always negative
POLYTHENE IS MEAN
What happens if you rub a neutrally charged balloon onto a neutrally charged jumper
- causes friction which causes electrons to move
- leaving one negatively charged and the other positively charged
- so they will stick
- because opposites attract
What happens if you hold a negatively charged balloon next to a neutrally charged wall
- it would stick
- because the electrons in the balloon and the wall will repel
- inducing a positive charge in the wall
- and opposites attract
Describe how a dust print lifter works
- lifting sheet is placed over footprint
- metal plate is placed near it
- a control unit connecting both applies a voltage between them
- lifting sheet = negative, metal plate = positive
- The electrons in the dust repel away from their like charges leaving the protons to attract to the paper
Describe how a photocopier works
- an area of a cylindrical drum is given a positive charge
- light is projected and an image is formed on this area so that the charge only stays on the shape that is to be printed
- toner (negatively charged) is dropped onto the drum, sticks to charged areas
- excess toner is removed
- paper is pressed against drum
- paper is heated to melt toner which forms the permanent image on the paper
How to prevent sparks/explosions when refuelling aircraft
Earth the plane using a conductor allowing the charge that built up to flow to earth.
Uses of electrostatics
Paint spraying, photocopier, crop spraying(insecticide is sprayed)
Dangers of electrostatics
Lightning, refuelling aircraft,
Describe how lightning works
A build up of positive charge accumulates on the ground beneath the cloud attracted to the negative charge in the bottom of the cloud. If the difference in the charges is enough, lightning will strike that place
Symbol for current in an equation is … and is measured in …
I Capital i
Amperes (Amps) A
what is Current
the rate of flow of charge
State the equation linking current time and charge & then the symbols then the units
Charge = current x time
Q = It
Coulombs = Coulombs/second x seconds
What is the difference between a distance-time graph and a displacement-time graph
Displacement graphs are able to show direction aswell whereas distance graphs tend not to
what is velocity
Speed with a direction
Eg. v = -10m/s v = 10m/s
SPEED for both is 10m/s
VELOCITY adds + or - depending on direction
What does the gradient on a distance-time graph show
Velocity
Equation to find ACCELERATION and then symbols
acceleration = final velocity-initial velocity / time
What is acceleration
the rate of change of velocity
State the equation linking time distance and velocity
Distance = velocity x time
How do you work out the distance travelled on a velocity-time graph
Find the area under the line
Basic facts about Ticker Timers
Time taken between each dot is always the same
The distance varies depending on speed
What is a vector quantity
A vector quantity has both direction and magnitude
What is a scalar quantity
A scalar quantity has only magnitude
Give some examples of vectors
Acceleration
Current
Displacement
Moment
etc
Give some examples of scalars
Charge
volume
Time Temperature
etc
What is displacement
How far you move in a given direction
State the equation linking mass acceleration and force and symbols then units
Force = mass x acceleration
F = MA
N = kg x m/s*2
Describe Newton’s 3 laws
- if there are no forces acting on an object which is not moving, it will stay at rest. If it was already moving at a steady state in a straight line then it will continue to move as before
- If a force is applied to an object then it will change its speed in the same direction as the force
- For each force there is another force acting in the opposite direction with the same strength
Give four methods to investigate motion
light gate
ticker tape
motion sensors
stopwatch and tape measure
What is weight and what is it measured in
The force of attraction an object feels towards another object. Newtons (N)
What is Mass and what is it measured in
The number and type of atoms in an object. (Kg)
State the equation linking Gravitational field strength, mass and weight and the symbols
Weight = mass x gravitational filed strength
W = mg
What equation is the same as W = mg
F = ma
What equation is the same as F = ma
W = mg
State the equation linking Braking distance, Thinking distance and stopping distance
Stopping Distance = Thinking distance + Braking distance
Thinking distance is affected by
Alcohol
Tiredness
Braking Distance is affected by
Worn down tires/brakes
Slippery surface (weather)
Angle of surface (Hill)
Explain terminal velocity
- At the start = only one force = weight so accelerate
- A slip second later, air resistance will be acting the other way but as the forces are unequal, acceleration
- As acceleration increases, air resistance increases
- Air resistance keeps increasing until it becomes equal to the weight of the object and
- so the resultant force is 0
- so he will reach his terminal velocity and travel at a constant speed
how to find acceleration on a velocity-time graph
gradient
what would to an object with balanced forces acting on it
it will stay at rest or stay in constant motion as its resultant force is 0
what would happen to an object if an unbalanced force was acting on it
- the direction of the object’s acceleration is the same as the direction of the unbalanced force
- the magnitude of the object’s acceleration varies in direct proportion with the size of the unbalanced force
four ways to investigate motion
- motion sensors (reflected sound)
- ticker tape
- light gate
- stopwatch and tape measure
what is mass
the number and type of atoms in an object (kg)
what is weight
the force of attraction an object feels towards another object (typically a planet/star) (n)
difference between normal reaction force and upthrust
normal reaction force happens ALL the time whereas upthrust only happens in fluids
practical to find speed
use a ticker tape timer attached to a trolley pulled across a bench/down a ramp
(normally 50 dots per second)
is force a scalar or a vector quantity
vector
friction is a force that opposes ……..
motion
equation to find force
f = ma
equation to find wieght
W = mg
equation to find stopping distance
stopping distance = thinking distance + braking distance
factors that affect a vehicle’s stopping distance
- speed
- mass (momentum)
- road condition
- weather
- brake pad age and wear
- inebriation
- reaction time
describe how terminal velocity is reached
Immediately on leaving the aircraft, the skydiver accelerates downwards due to the force of gravity and his weight. There is no air resistance acting in the upwards direction, and there is a resultant force acting downwards so the skydiver accelerates towards the ground.
As the skydiver gains speed, their weight stays the same but the air resistance increases. There is still a resultant force acting downwards, but this gradually decreases.
Eventually, the skydiver’s weight is balanced by the air resistance/friction. There is no resultant force so there is no more acceleration and the skydiver reaches terminal velocity.
state the equation linking force, sprint constant and extension
force = spring constant x extension
what is Hooke’s Law
within the elastic region, extension is proportional to the force applied
what is elastic behaviour
when a material returns to an original size and shape when you remove the forces deforming it
what is plastic behaviour
a plastic material is one that stays deformed after you take the force away
how can you explain the initial linear region of a force-extension graph
using Hooke’s Law
what is Newton’s third law
whenever two objects interact, they exert equal and opposite forces on each other.
(a skateboarder pushing another and they both move at the same acceleration away if they are at the same mass because f=ma. if one skateboarder is double the mass of the other he will move away half as far)
equation for moment
moment = force x perpendicular distance form pivot
where does the weight of a body act
through its centre of gravity
the upward forces on a light bean, supported at its ends, vary with ……
the position of a heavy object placed on the beam
what is spring constant
measures how stiff the spring is
in what ways can forces affects other objects
- speed them up or down
- change their shape
- change their direction
newtons first law
an object remains in the same state of motion unless a resultant force acts on it.
newtons second law
f = ma
how to find a 2D shape’s centre of gravity
Put a pin attached to a freely hanging string into the freely hanging shape and draw a line where the string hangs
- put the pin in other random places along the edge of the shape and where they meet is the centre of gravity
How to measure the speed of an object using light gates
the vehicle must have a card attached to the top (an interrupter) in order to break the beam.
- then lets say the interrupter take 0.02s to pass through the gate, if the interrupter is 10cm then the speed (=distance/time) is 5m/s
what does the gradient tell you on a velocity-time graph
acceleration
what does the area under a velocity-time graph tell you
distance travelled
what is the relationship between: final speed, initial speed, acceleration, and distance moved
v^2 = u^2 + (2 x a x s)
experiment to investigate the motion of a toy car on a ramp
How long is the bus stationary
10 secs
What is Hookes law
extension is proportional to the amount of force applied up to the limit of proportionality
when a skater throws a snowball, she slides backwards on the ice. explain why she moves in that direction
- newton’s third law - every action has an equal and opposite reaction
- so forces are acting on both the snowball and the skater
- and they are equal and opposite
- so the rate of change of momentum is the same for both forces
in what three ways can forces affect bodies
- speed - speed up or slow down
- direction - change direction of travel
- shape - stretch, compress, or deform
what region of a force-extension graph is associated with Hooke’s law
the initial linear region
how do you calculate the momentum of a car after a crash
conservation of momentum
what is Newton’s third law
Whenever two bodies interact, the forces they exert on each other are equal and opposite
