Further Mechanics Flashcards
What does the momentum of an object depend on?
mass & velocity
What is the product of the two values of mass and velocity?
momentum of an object
The word equation for linear momentum is:
mass x velocity = linear momentum
The symbol equation for linear momentum is:
p (in kg ms^-1) = m (kg) x v (in ms^-1)
Is linear momentum a vector/scalar quantity?
vector
Is velocity a vector/scalar quantity?
vector
Is mass a vector/scalar quantity?
scalar
A vector quantity means that something has…
size (magnitude) and direction
A scalar quantity means that something has…
only size (magnitude)
Assuming no external forces act…
momentum is ALWAYS conserved.
The total momentum of two objects before they collide =
the total momentum after the collision.
Collisions can be…
elastic or inelastic.
An elastic collision is where…
momentum is conserved and kinetic energy is conserved.
No ………… energy is conseved
What happens in an inelastic collision?
Some energy is dissipated as heat/light/sound etc.
What is the difference between kinetic energy before a collision and the kinetic energy afterwards?
The energy dissipated as heat/sound etc.
What is Newton’s 1st Law?
If a body continues in its state of rest or uniform (unaccelerated) motion in a straight line unless acted upon by some resultant external force.
What is the resultant force acting on a body if it is not accelerating?
Zero.
When is the resultant force zero?
When a body is moving at a constant speed in a straight line or when is not moving.
Just because the resultant force is zero,…
it does not mean that there are not any forces acting upon it.
The 1st law also expresses the idea of what?
inertia
What is inertia?
The reluctance of a body to start or stop moving / for its motion to be changed.
A body of large mass is difficult to start or stop and therefore…
it has a large inertia.
The mass of a body is a measure of:
its inertia.
Linear momentum is what?
like, inertia it is a measure of resistance to change of motion.
If 2 bodies of different masses have a common velocity. Which is more difficult to stop/slow down?
The heavier one.
Newton’s 2nd Law is?
“The rate of change of momentum is directly proportional to the resultant force acting on the body and it takes place in same direction as the force.”
resultant force (F) = mass (m) x acceleration (a) when mass is what?
constant
resultant force =
mass x acceleration
ma = what?
the resultant force of an object
the vector sum of all the forces adds up to make the….
resultant force.
Force is measured in:
Newtons (N)
Mass is measured in:
Kilograms (kg)
Acceleration, (a) is always measured in:
metres per second per second (ms^-2)
Acceleration is always in the …… direction as the …….. force.
SAME
resultant force
Impulse =
change in momentum
F = (mv - mu)/t means what?
rate of change of momentum
Impulse is defined through symbols as:
Ft (force x time)
Units of impulse are:
Newton seconds (Ns)
On force-time graph, how is the impulse found?
the area underneath the line
What is Newton’s 3rd law?
If body A exerts a force on body B then body B exerts the equal but opposite force on body A. (ie: action force and reaction force are equal but opposite)
mass flow rate =
mass / time (m/t)
mass = volume x density (in symbols?)
m = Vp
volume = area x length (in symbols?)
V = AL
resultant force equation (NOT on formula sheet)
pAv^2
volume flow rate =
V/t and vA
if something is energy/time what do you need to work out (not energy)
POWER
on a stress/strain graph what does the steel line look like?
diagonally straight up then curved, goes higher up than rubber (like an r)
on a stress/strain graph what does the rubber line look like?
almost vertically straight then curves up
how much does Giga mean x10 to the?
9
how to convert cm^3 into m^3
x10^-6
in an elastic collision what is the impulse equivalent to?
2mv
change in momentum =
mv [final] - (-mv) [initial]
what does circular motion describe the motion of?
a body travelling at a constant speed in a circular path
arc length =
rθ
360° = how many radians?
2π
in Physics what can’t you leave the the distance of arc length in?
radians. MUST convert into number (3sf)
what is angular velocity?
the Rate of Change of an Angle
what is rate of change of an angle measured in?
rad s^-1
what is angular speed?
the speed and angle rotates through per second
linear speed is measured in?
ms^-1
symbol for angular speed?
ω
ω is measured in what?
rads s^-1
