P5 Forces Flashcards
Vectors vs Scalar quantities
Forces are vector quantities they have MAGNITUDE and DIRECTION they represtented by an arrow (e.g force velocity acceleration)
Scalars only have MAGNITUDE
Contact vs Non- Contact
Contact has to be TOUCHING (e.g frcition, air resistance, tension)
Non-contact doesnt (e.g magnetic, gravitational, electrostaic)
When two objects INERACT both objects have a forced produced ( ground pushes on chair, chair pushes on ground)
What’s mass?
How much ‘stuff’ is in the object will REMAIN THE SAME anywhere
What’s weight?
The force acting upon an onject due to GRAVITY- will vary depending on planet for example as it’s causedby the GRAVITATIONAL FIELD STRENGTH
Equation for mass GFS and Weight
Weight (N) =Mass (kg) x GFS (N/kg)
DIRECTRLY PROPORTIONAL
How do free body diagrams work?
arrows show direction, size of arrows show magnitude
What is a resultant force?
the overall force on an object or point ( e.g 1200N to the left- 1000N to the right= a resultant force of 200N to the LEFT)
If a resultant force moves an object WORK IS DONE and ENERGY IS TRANSFERRED
How to calculate work done?
Work Done (J)= Force (N) x Distance (m)
How to reach equilibrium?
If all forces combine to a resulatnt force of 0
How does elastic deformation work?
more than one force acting, work is done causing energy to be transferred to the objects elastic pontential store- it can go back to its origional shape- these are ELASTIC OBJECTS ( e.g a spring)
How does inelastic deformation work?
if it doesn’t return to it’s original shape and length after the force has been removed.
Extenstio and force- whats the limit of proprotionality
they are DIRECTLY PROPORTIONAL
Force=spring constant x exstention
a stiffer material has a greater spring contant
BUT when the force is great enough this STOPS working this is the LIMIT OF PROPORTIONALITY
PRACTICAL investigating springs
Method;
1) measure the NATURAL LENGTH of the spring with a mm ruler that’s clamped to the stand take the reading at eye level
2) add mass to the spring and allow to REST record this new length the EXTENSION is the CHANGE in length.
3) REPEAT until you have enough meauremnts (>6)
You can use the measurments to work out energy stored;
Eleastic = 1/2 spring x extention
Potnetial energy constant
Ee=1/2ke^2
Whats a moment
The turning effect of a force
size of moment:
M=Fd (force x distance)
1) the force of the spanner causes a turning effect on the nut (which acts as a PIVOT). A larger force or longer distance would= a LARGER moment
2) To get the MAXIMUM moment you need to push at RIGHT ANGLES
Blanaced moments
The total anticlockwise moment= the clockwise moment about a pivot if the ibject is BALANCED
Whats a lever
they make it easier to do work- they INCREASE the DISTANCE meaning less force is needed to get the same moment
What are gears
They trasmit rotational effects- theyre cirlcuar dics with ‘teeth’ around them. these interlock
different sized gears can change the moment of the force as a force transmitted to a larger gear will cause a bigger moment because the distance to the pivot is GREATER
a larger will turn SLOWER than a smaller one
whats a fluid
equation for pressure in fluid
a substance that can flow because their pasrtciles can move around- these particles collide meanin pressure if exerted
P=F/A
pressure(Pa)=Force(N)/ Area m^2)
pressure in LIQUIDS with depth and density
pressure in a LIQUID depedns on the depth and desnity, the more dense the more particles the more collisions= higher pressure, same with depth basicially.
P=hpg
pressure(pa)=hight(m) x density(kg/m3) x GFS 9N/kg)
whats upthrust
pressure increases with depth so the force exterted on hte bottom of the object ius larger than the force actiang on the top making a RESULTANT force of UPTHRUST
the upthrust is EQUAL to the WEIGHT of the fluid that ahs been displaced THE PINEAPPLE
what happens if an objects weight=upthrust?
It floats- as the forces have balanced. if the objects weight > upthrust then it sinks
Meaning if if floats or not depends on its density
whats atmospheric pressure
created by air molecules in thr atmophere colliding with the surface
it decreases with hieght
difference between diatnce and diplacemnt
distance is SCALAR just how far somehtings moved
displace,ent is a VECTOR
speed vs velocity
speed is SCALAR just how fast your going
velocity is speed and direction its a VECTOR
distance travelled (m)= speed (m/s) x time (s)
typical speed of a person wlaking
1.5 m/s
person running
3 m/s
person cylcing
6 m/s
car speed
25 m/s
train speed
55 m/s
plane speed
250 m/s
whats acceleration
(and deceleration)
how quickly your speeding change in veolicty over an amount of timr
acceleration=change in velo/time
m/s2, m/s, t
dceleration is just the opposite of this
whats uniform acceleration
basisically comtasnt acceleration
rules for distance-time graphs
gradient=speed
flat=stationary
straight uphill=steady speed
curves=acceleration/de
steeping curve=speeding up
levelling off curve=slowing down
find speed with a tangent if neccisary
rules for velocity-time graphs
gradient=acceleration
flat=steady speed
steeper=freater accel/deccel
area=distance
whats friction
if an obkject ahs no force it will always be stooppoed by friction, it acts in the OPPOSITE direction to movement.
whats drag and air resistance
resistance in a fluid
air resistance is a type of drag
parachutes WANT drag to DECREASE drag we make things STREAMLINED
drag increases with speed
whats terminal velocity
when falling objects start the force of gravoity is stronger than frcition meaning they accelerate
as speed increases so does the friction
until the resultant force is 0
this is the terminal velocity its maxiumum speed
what two factors does terminal velocity depend on?
shape and area they affect teh frcition
what do newtons first and second laws state
if the resultant force on a stationary object is0, the object will remain stationary. if the resultant force on a moving onject is 0 itll just carry on moving at thr same velocity.
acceleration is proportional to the resultant force
