Forces Flashcards
what is the equation for speed?
v = s / t
how do you find the distance on a velocity time graph?
distance is the area under the graph
what are the units for accelaration?
m/s ^2
when do you use the equation v^2= u^2+2AS
for any question that uses constant accelaration
what is stopping, thinking and braking distance?
stopping distance is the distance needed for a car to stop at a given speed
thinking distance is the distance we travel in the time it takes for us to react to the situation
braking distance the distance travelled after you start braking
what are some factors affecting thinking distance?
tiredness
distractions
alcohol
old age
drugs
what are some factors affecting braking distance?
bad condtions of the brakes
greater speed
mass of the vechicle
bad condition of the vechicle
icy/wet roads
what happens during braking?
brakes apply a force to the wheels and then the brakes use frictional forces
brake discs and shoe heat up
the vechicle comes to a stop
what are some contact and non-contact forces?
contact-
friction
air resistance
tension
gravity
electrostatic force
magnetic force
what is a vector quantity?
give some examples
a vector quantity is a quantity that has both magnitude and direction
velocity
force displacement
accelaration
what is a scalar quantity?
give some examples
a scalar quantity is a quantity that tells you only magnitude
distance
speed
length
mass
how do you draw a vector diagram?
arrow pointing in the correct direction at correct angle with scale clearly written
what is a resultant force?
the overall effect of more than one force
how do you represent resultant forces graphically?
draw your vectors and connect ends of both arrows to form a rectangle
draw an arrow to the corner and measure and label your angles
measure resultant force using the convert scale
what is newtons first law of motion?
on object in motion stays in motion at a constant velocity and straight line unless acted on by an unbalanced force
what is inertia?
the tendency of an object to resist changes in their state of motion
how does mass effect inertia?
an object with a larger mass is has a greater tendency to resist changes in its state of motion
what is newtons second law of motion?
the accelaration of an object is directly proportional to the force applied to it and inversely proportional to its mass
what is mass measure in?
kg
what is newtons third law?
for every action there is an opposite and equal reaction
how are mass and weight different?
mass never changes, you have the same mass anywhere in the universe
weight does change depending on the strength of the gravitational field strength acting on your mass
what comnditions are needed for terminal velocity?
balanced forces
zero accelaration
constant velocity
if a skydiver jumps out of a plane why does the upward force increase as he falls?
becuase air resistane is directly proportional to the velocity and as he is falling gravity is pulling him closer so his speed increase meaning air resistance does as well
what is directly proportional to velocity when an object falls?
air resistance
what is terminal velocity?
when an object moves with zero accelaration and constant velocity
this means the forces are also balanced
what are the units for extension?
metres
what are the units for the spring constant?
n/m
what does it mean if something is elasticly deformed?
the object will return back to its normal shape
what do we see if an object does not return back to its normal shape?
it has been deformed
what is inelastic deformation?
when the object does not return back to its normal shape
what is the limit of proportionality?
where inelastic deformation happens and it starts to disobey hookes law
what is hooke’s law?
the extension of a spring is in direct proportion with the load added as long as the load does not exceed the elastic limit
what is a moment?
the turning effect of a force around a pivot
what does the size of a moment depend
on?
the force (weight) acting
the perpendicular distance from the pivot
what makes something more stable?
being closer to the ground and having a wider base
what are gears?
rotating wheels with teeth that interlock used to transmit or multiply rotational forces
what does a low gear do?
gives a low speed but a high turning effect
how can you find the centre of mass of a material?
suspend the material freely from a stand
attach plumbline and draw the line of action of mass
rotate the material and suspend again this time from a different point
once again use the plumbline to draw the line of action of mass
where the two lines meet is where the centre of mass is
what is work done also known as?
energy transfered
what are the units for work done/energy transfered?
Joules
What are some times where we can tell no work has been done?
when a force is exerted but the object dosent move
when an object is carried at a constant velocity by a force perpendicular to the motion no work is done
what is 1 watt equal to in terms of energy transfered?
1 joule of energy per second
what are the units for momentum?
kgm/s
what is the law of conservation of momentum?
momentum before = momentum after as long as no external forces are acting
how is the momentum changes in a front end and rear end impact?
in a front end impact the momentum is reduced reduced
in a rear end impact the momentum of the car is increased
