motion, forces and energy Flashcards
what is a vector
measurment of displacement
what is scalar
dont consider direction, only distance
formula for velocity
v=s/t
what is velocity?
speed in a given direction
formula of speed
s=d/t
acceleration of free fall g for
an object near to the surface of the Earth is
approximately constant and is approximately
9.8m/s2
what is acceleration
a= change in velocity/ time taken
speed time graphs: a flat horizontal line at zero speed =
stationary
speed time graph: a flat horizontal line above zero speed
constant speed
speed time graphs: an upward sloping line =
accelerating; the steeper the gradient, the higher the acceleration
speed time graphs: a downward sloping line =
decelerating.
what is terminal velocity
the top speed of any object enperiencing air resistance or any similar friction force
what is mass
a measure of the quantity
of matter in an object at rest relative to the
observer
what is weight
t weight is a gravitational force on an
object that has mass
what is gravitational force
force per
unit mass
g = weight/mass
and know that this is equivalent to the
acceleration of free fall
what is density
mass per unit of volume
p= m/ v
how to measure irregular shapes
add the irregular shap to water and measure the loss of water. this will be the volume of the object. use the formula p=m/v to calculate the density
when will an object float
when it is less than 1g/cm3- or a density less than the liquid it is fut in
forces can change the ……. of an object
change its shape
change its size
change its velocity
change its direction of motion
what the formula of force
force (N)F=mass (kg) × acceleration (m/s2)=ma
what happens when force moves in a circular motion
force is pointed to the centre of the circle
what is resultant force
the net force: delta of 2 forces
what is force formula for stretching
f= spring constant x extension
k=force/x
what is limit of porportionality
the limit of force a spring can take before it doesnt go back to its original way
motion in a circular path
due to a force perpendicular to the motion as:
(a) speed increases if force increases, with mass
and radius constant
(b) radius decreases if force increases, with mass
and speed constant
(c) an increased mass requires an increased force
to keep speed and radius constant
what is solid friction
force between two
surfaces that may impede motion and produce
heating
what is the moment of a force
measure of
its turning effect
examples: opening a lid jar
moment= force x perpendicular distance from the pivot
when is an object at equilibrium
when there is no resultant force
what is the centre of gravity
It is the average position of all the mass in that object
how to determaine the centre of gravity of a irregular shaped plane
1) Cut out an irregular shape of card.
Make a hole near the edge of the shape and place a pin through it.
2) Clamp the pin so that it is horizontal, and make sure the card can rotate.
3) Tie a mass suspended by cotton from the pin. This must be free to swing backwards and forwards like a pendulum.
4) Once the cotton and card have stopped moving, carefully mark where the cotton is aligned on the card by drawing a line along its length (shown as a black solid line in Figure 2).
5) Repeat this procedure for three different positions
the centre of gravity will be where the point intercect
what is momentum
mass x velocity
what is impulse
force x time
conservation of momentum
In any collision, the total momentum before and after the collision is the same
what is the resultant force in momentum
change in
momentum per unit time; r
F = ∆p/
∆t
