Forces for y11 mocks Flashcards
what is a force
a push or pull that acts on an object due to an interaction with another object
what are some contact forces
-friction
-air resistance
-tension
-normal contact force(force that acts against stationary weight)
what are some non contact force
gravitational
magnetic
electrostatic
Is air resistance a contact or non-contact force? Explain why.
Air resistance is a contact force. This is because it is due to the physical contact (collisions) between an object and the particles in the air.
what are examples of scalars
speed
time
mass
distance
what are vectors
velocity
force
momentum
displacement
acceleration
Is power a vector or a scalar quantity? Explain your answer.
Power is a scalar quantity because it only has a magnitude (how many watts), it doesn’t have a direction.
what are free body diagrams and what do they contain
diagrams that show all the forces acting on an object
what is the resultant force
the overall force on an object.
for an object to stay still what must happen +an example
more than 1 force must be applied
eg:squishing ball on floor
floor pushes ball up
what are the 2 types of deformation(change of shape)
elastic(object returns back to og shape when force is removed)
inelastic(stays deformed)
how can we measure extension
measure how springs length changes as downwards force is applied(mass)
relation between f and e
f is directly proportional to e
higher spring constant
stiffer the material/less elastic
what is hookes law
f(N) and e(m) are directly proportional
what are the things that can happen to an object if a force is applied
stretch, compress, or bend
what is elastic potential energy
energy transferred to an object as it is stretched
what is the spring constant/elastic potential energy on a force / extension graph
-gradient on the straight part of the graph
-elastic potential energy
what is the limit of proportionality
where the object stops obeying hookes law
when a stretched object is released what energy is the epe transferred to
kinetic energy
what are the speeds of common objects and average people
walking:1.5m/s
running 3m/s
car 30m/s
what is the rate of change in velocity/acceleration
how quickly something speeds up
what can acceleration in the 2 equations be assumed as
9.8m/s
what is gradient on a distance time graph
speed
curved upwards and curved downwards means the tangent will be
upwards:tangent bottom
down:tangent above
On a distance / time graph, the distance is on the ?
-axis and the time is on the ?
-axis.
distance:y
time:x
curve steepens means
object is accelerating
what is the gradient of a velocity time graph
acceleration
area under curve=
distance travelled
how to find distance travelled on velocity time graph
count squares under graph
what is terminal velocity
where velocity remains constant
what does the size of the air resistance depend on
the number of collisions which depends on the sa of the person and velocity
what happens when the diver reaches terminal velocity
resultant force between air resistance is 0
what happens when the diver pulls out a parachute at terminal velocity
surface area will increase hugely so air resistance will increase making resultant force be in the upwards direction but as they slow down until resultant force reduces until 0
what is newtons 1st law
resultant force is required to move object
what is newtons 2nd law
if non 0 force acts on an object it will accelerate
rf=ma
what is inertia
unless acted on by rf objects at rest will stay at rest and objects in motion will remain at motion
what is inertial mass
mass=force/acceleration
what is newtons 3rd law
when 2 forces interact the forces they exert on each other are equal and opposite
what is the force exerted on you if you push a box
normal contact force
what is the energy stored in a force extension graph
the area under the graph
what is the moment
turning effect of a force
moment equation
M(Nm)=f(N)xd(m)
what is the distance in moments
perpendicular distance from line of action to the pivot
3 ways we can increase moment
larger force
longer distance object(eg spanner)
pushing at right angles
what makes an object balanced and unable to turn
if total anticlockwise moment=total clockwise moment
what do moments allow us to do in mechanical devices
they help transmit forces across a distance and get the most out of a small force
what do levers do
make it easier for work to be done(eg lift load)
how do levers make it easier for us to do work
they increase the distance from the pivot where the force is applied so less force needed for the same moment
how do levers affect force and moment
less force needed for the same moment
eg of simple levers
long sticks and bars
wheelbarrows
what do gears do
transmit rotational effect from one place to another
what are gears
circular disks with teeth around their edges
when gear teeth interlock what happens
turning one causes the other to turn in the opposite direction
what is meant by transmitting the turning effect of a force
converting and input force to an output
if input and output are on the same side/diff side of pivot what happens
they act in same direction-wheelbarrow
they act in opp directions-scissors
why is the output force larger than the input
output is closer to the pivot
