P2.2 -Forces Flashcards
what happens in an interaction pair (N3)?
- forces act in opposite directions
- each force is the same magnitude
what is newton’s third law?
“when two bodies interact, they exert a force upon each other that is equal in size, but opposite in direction”
state three non-contact forces?
- gravity
- electrostatics
- magnetism
how does gravity interact with objects?
attracts them
how do electric charges interact with objects?
- attract and repel
what is a field of a force?
the region where an electric charge, a magnetic material or a mass experiences a force
how are forces represented?
with a force arrow
where does a force arrow start on an object for a non-contact force?
the centre
where do you draw contact force arrows from?
the point of contact
use what you know about the structure of the atom to suggest why a non-contact force is produced within an atom
- there are electrons on the outsides of atoms.
- As you push them together they repel.
- This is an electrostatic force, which is a non-contact force.
what is terminal velocity?
the velocity at which a body falls through a medium, when the drag acting on the body is equal to its weight
what planes do we consider when explaining the motion of an object at an angle?
- the plane perpendicular to the slope
- the plane parallel to the slope
what is air resistance?
when an object moves through air and collides with other air molecules
what is tension?
the pulling force that a string or cable exerts when something or someone pulls in it
what is friction?
- when two surfaces are touching and try to move against each other.
how does friction work?
- Tiny bumps in the surface interlock (overlap or fit together). This creates a frictional force that opposes their motion.
what kind of force is air resistance?
contact (air particles collide)
what does a free body diagram show?
shows the forces acting on a single object
what is a resultant force?
the force when two or more forces are added together
what is a force?
a push of a pull
an attraction or repulsion
what can a force do?
- change the shape of an object
- change the motion of an object
what are forces measured in?
N (newtons)
state one way in which the force of gravity is different to the electrostatic force
- gravity can only attract
- electrostatic force can attract and repel
what happens when bodies interact?
- exert forces upon each other
what does a free body diagram show?
all the forces acting on a single body
what does it mean to resolve a force?
- work out how much of it acts in the horizontal plane
- work out how much of it acts in the vertical plane
what is Newton’s First Law?
“A body will remain at rest, or continue to move at a uniform velocity, unless acted upon by a resultant force”.
what is Inertia?
A measure of how difficult it is to change the velocity of a body (either from rest or when traveling at a uniform velocity)
if an object has a higher mass, why does it have a higher inertia?
- more difficult to accelerate/change velocity
what is componenticing?
seeing how much force is acting on specific planes
what is the equation for force?
F = M x A
newton’s second law
what is the unit for acceleration?
m/s^2
meters per second squared
define acceleration
the rate of change of velocity of a body
if a body is travelling at a constant speed but a different direction, is it accelerating?
yes, as the velocity changes
what is the equation for acceleration?
final velocity - initial velocity / time
what does acceleration depend on?
- size of resultant force
- inertia (mass) of object
what stays the same during circular motion?
- speed of the plane stays the same
what changes during circular motion?
velocity continuously changes (direction)
why is an object in circular motion continuously accelerating?
as it is constantly changing direction
where does the centripetal force act?
towards the centre of the circle
what does centripetal force change?
- the direction of velocity
- NOT SIZE
what is free fall?
the fall of a body through a medium, without a drag producing device
explain why terminal velocity is a constant
the weight of the body is balanced by the drag force acting upon it
which planes are considered for a box on a slope?
- parallel to slope (where box tries to accelerate)
- perpendicular (where normal reaction force acts)
what is the equation for momentum?
mass x velocity
what is momentum a measure of?
how difficult it is to stop a moving body
what is momentum measured in?
kgm/s (kilograms meters per second)
what does momentum depend on?
- mass
- velocity
is momentum vector or scalar
vector (has direction)
what is the law of conservation of momentum?
the movement before is equal to the momentum afterwards
what is an inelastic collision?
when energy is transferred to other sources
what is an elastic collision?
when no net energy is transferred to other sources (which is not kinetic energy)
ie. no energy lost as sound, light
what happens when a stationary body is hit by a moving body
two bodies move off together
what is the opposite force to the force of the Earth on a skateboarder
normal reaction force
force of skateboarder on earth
what happens when two bodies push off each other?
bodies move away from each other
what is work?
the transfer of energy
what is work measured in
J (joules)
what happens when work is done?
energy is transferred from one form to another
what happens when you lift a body?
kinetic energy is transferred to gravitational potential energy
what is the equation to calculate work done?
force x distance
how much is one joule in newton meters?
1J = 1Nm
what do we assume about distance?
it is covered at a constant velocity
(zero acceleration)
(zero resultant force)
how does friction transfer energy?
out of a body (and transfers heat)
what is power?
rate of transfer of energy
how does a force applied transfer energy?
into a body
what is the equation for power
energy / time
what is power measured in?
Watts(W)
how much energy is transferred during 1 watt (per second)
1 joule per second
how is acceleration proportional to mass?
inversely proportional
what is Newton’s Second Law?
“The acceleration experienced by a body is directly proportional to the resultant force acting upon it, and in the same direction”
AKA
‘push something harder, accelerate faster’
