P2.3 (1) - forces in action Flashcards
p2.3.1 - p2.3.3 (spec approved)
what are elastic bodies?
objects that return to original shapes when the deforming force is removed
what are plastic bodies?
objects that do not return to their original shape when the deforming force is removed
state hooke’s law
the extension of a body is directly proportional to the force applied, as long as the limit of proportionality is not exceeded
what is the equation for hooke’s law?
force = spring constant x extension (N) = (N/m) x (m)
F = K x E
how can the spring constant be found from a force-extension graph?
from the gradient
where does the limit of proportionality lie on an extension-force graph?
just before it begins to curve
what is the elastic limit?
the like middle point
- if exceeded, spring is permanently deformed (even when force is removed)
- below limit, spring returns to original length
where is the elastic limit on a force-extension graph?
just after the limit of proportionality
what is the spring constant a measure of?
the stiffness of a spring
if a spring is very stiff, how is the spring constant?
higher
what is the equation to figure out the work done while stretching a spring?
energy (J) = 0.5 x spring constant (N/m) x (extension (m))^2
what is the work done while stretching a spring also known as?
elastic potential energy
can you use an elastic band instead of a spring when using a newton-meter, and why?
no, as it does not obey Hooke’s law (as it has a non-linear relationship between force and extension)
why is a rubber balloon hard to blow up at first (picture graph in your head)?
as rubber does not follow hooke’s law.
so at the beginning the gradient is very high, meaning more force is applied to increase its extension
describe the relationship between glass and force and extension
it has a linear relationship (straight line), but a very steep gradient - as it is a stiff material
what prevents tennis rackets from being deformed when hitting a tennis ball?
they are specially designed to transfer energy back, rather than storing them when they deform
what causes materials to deform?
storing too much energy
what is elastic potential energy?
energy stored by an elastic body (that has been stretched)
how is a rubber band able to revert back to its original shape when the force is released? (energy)
converts elastic potential energy to kinetic energy (and so it moves)
define a field
a region of space within which a body experiences a force
where would you find a gravitational field?
around anything with mass (infinite)
where would you find a magnetic field?
around any magnet
where would you find an electrostatic field?
around anything that is charged
do fields exert the same force on every body?
no, it depends on how much mass/charge/magnetism the body itself has
what is the unit for gravity?
n/kg
what is weight?
The force of the Earth on an object (acts downwards)
what is gravitational field strength a measure of?
the force on 1kg of mass in a gravitational field (due to another mass)
what is the equation to calculate gravity constant?
mass x gravitational field strength
what is gravitational potential energy?
The energy transferred to a gravity store when you lift an object in a gravitational field
equation for calculating gravitational potential energy
(J) = mass (kg) x height (m) x gravitational field strength (N/kg)
what has to be present to stretch, bend or compress an object?
more than one force must be present + applied
what is the difference between linear and non-linear relationship between force and extension?
linear relationships obey hooke’s law, non-linear relationships do not obey hooke’s law
how would a gravitational field differ with mass?
greater the mass, greater the gravitational field around it
what is the acceleration in free fall?
10m/s^2
