test 1 Flashcards
A ruler (rule) is used to measure
the length of an object between 1mm and 1m.
The volume of an object of irregular shape can be measured by
placing it into a measuring
cylinder full of water. This causes the water level to rise, and this rise is equal to the volume
of the object.
A micrometer screw gauge is used to measure
very small distances that a rule
cannot measure
Analogue and digital clocks and devices are used to measure
Time intervals
speed
distance traveled per unit time
If speed of something is changing it is
accelerating (if increasing) or decelerating (if decreasing)
Average speed =
total distance/ total time
Distance is measured in
mm, cm, m or km
time is measured in
ms, s, minutes or hours
velocity
speed in a given direction
acceleration
rate of change of velocity
Acceleration =
change in velocity/ time
In a distance time graph the gradient is
velocity
Negative gradient in a distance time graph is
returning to the starting point
In a distance time graph a curved line means that the
velocity is changing
and it is accelerating.
in a speed time graph the gradient is
Acceleration
negative gradient is
Deceleration
if the speed is zero it is
At rest
a horizontal line means
Constant speed
a curved line means
The acceleration is changing
mass is a measure of
how much matter is in an object
Weight is a
gravitational force measured in newtons
the gravitational field strength on earth is
10Nkg
Weights (and hence masses) can be compared using
A balance
Density
mass per unit volume
density =
Mass/volume
to find the density of a liquid
Find the mass of the measuring cylinder by placing it on a balance, then fill it with the liquid
and measure the new mass. The difference in masses is the mass of the liquid.
The volume can be read from the cylinder and the density calculated using the equation.
To find the density of a solid
Measure the mass of the solid by placing it on a balance.
If the solid is regularly shaped, measure its dimensions using a ruler or other measuring
tool and then use a mathematical formula to find the volume.
If the solid is irregularly shaped, immerse it in water and measure the volume of the water
displaced. This is the volume of the solid.
Find the density using the equation.
Newtonβs first law states that an object has a constant velocity unless acted on by a
resultant force
Newtonβs second law states that
πππππ = ππππ Γ ππππππππππππ π = ππ
Newtonβs third law states that
every action force has an equal and opposite reaction force.
For example, the force of the Earthβs gravity on an object is equal and opposite to the force
of the objectβs gravity on the Earth.
Friction is a
force between two surfaces which impedes motion and results in heating. Air
resistance is a form of friction.
elastic deformation
The object returns to its original shape when the load has been removed, an
example being a spring being stretched under normal usage.
Plastic deformation
The object does not return to its original shape when the load has been removed,
an example being a spring that has been stretched too far.
hookes law states that
for a spring, πΉ = ππ₯ where F is the force applied to the spring in π, k is the spring constant in ππβ1
, and x is the extension in M
If elastic deformation is stretched to far it
wont go back to normal
If plastic deformation is stretched to far
it will break
The moment of a force is
a measure of its turning effect
moment of a force =
Force x perpendicular distance
moment = Fd
The pivot point is
the point which the object can rotate about
Equilibrium is when
there is no resultant force and it is balanced
Centre of mass is
the point at which all mass is considered to act
The wider a base is the
Harder it is for an object to topple over
a vector has
Magnitude and direction
a scalar has just
Magnitude
Examples of vectors
displacement, velocity, acceleration
Examples of scalars
Distance, speed, time
vectors can be represented by
arrows
Momentum
the product of mass and velocity
Momentum =
mass x velocity
p=mv
Impulse
product of force and time
impulse is equal to
change in momentum
Impulse =
Ft = mv - mu
Work done =
force x distance
Equation for work
W = Fd
Power is
rate at which energy is transferred or the rate at which work is done
Power =
energy transferred/time
Equation for power
p = E/t
Effencincy =
useful output/total input
