Topic 2 - Motion And Forces Flashcards
balanced force
when the result of all the forces on an object is zero
unbalanced force
non-zero resultant force on an object
Newton’s first law
an object at rest stays at rest and an object in motion stays in motion with the same speed, and in the same direction unless acted upon by an unbalanced force
when drawing a force how do you show the size of that force
length of the arrow
resultant force
the overall force acting on an object
how do you work out the resultant force if the forces are acting in the same direction
add them
how do you work out the resultant force if the forces are acting in opposite direction
subtract one from the other
centripetal force
the name given to these types of unbalanced force that causes circular motion
—> centripetal forces always act to pull an object into the middle of the circle
mass (kg)
the amount of a matter there is in an object
weight (N)
the force pulling on an object downwards
what’s the earths gravitational field strength
9.8N/kg (10N/kg)
weight equation
weight (N) = mass (kg) x gravitational field strength (N/kg)
what forces act upon a falling object
weight/gravitational potentional energy ⬇️
air resistance/drag⬆️
Newton’s second law of motion
non-zero resultant forces acts on an object, then it will cause the inject to accelerate
- the acceleration in the direction of a resultant force depends on: the size of the force, the mass of the object
circular motion
is a movement of an object along the circumference of a circle or rotation along a circular arc
why is an object that moved in a circular motion always accelerating
because although the speed remains constant, it’s always changing its direction as it moves round an object so therefore is always accelerating
(the centripetal force is always perpendicular to the direction the object is moving in circular motion)
equation to work out the force needed to accelerate a particular object
force (N) = mass (kg) x acceleration (m/s2)
Newton’s third law
for every action (force) has is an equal and opposite reaction
equilibrium in physics
if the size and direction of the forces acting on an object are exactly balanced, then there is no net force acting on the object and the object is said to be in equilibrium
what type of object does balanced forces act upon
the same
what type of object does an action-reaction force act upon
different objects
force
a push or pull that acts on an object due to the interaction with another object
-> forces are vector quantities because they have both magnitude and direction
what two things affect someone’s weight
mass and how strong the gravity is
terminal velocity
the maximum speed at which an object will fall
what happens to the forces in a collision
when two objects collide, they both exert a force on the opposite object; these forces are the same size but necessarily do not have the same effects on the two objects because they have different masses
momentum
a measure of how much motion an object has
momentum word equation
momentum (kg m/s) = mass (kg) x velocity (m/s)
momentum symbol equation
p = m x v
equation needed to work out the force used for momentum
force = change in momentum or mv - ma
time t
if you have more mass what does that mean for your momentum
objects with more mass have more momentum
conservation of momentum
when moving objects collide, the total momentum of both objects is the same before the collision, as is after the collision, as long as there is no external forces acting
thinking distance
the time for the driver to react to the problem while the vehicle travel some distance
breaking distance
the car will then travel a little bit more while the brakes are working to bring it to a halt
stopping distance
the overall sum (+) of the thinking and braking distances
reaction time
time person detecting a stimulus (e.g. flashing lights or a sound) and their response (e.g. pressing a button or applying brakes)
what can affect your reaction time
if the person is tired, ill answer has been taking drugs or drinking alcohol
what can distract you from a quick reaction time
your phone
what can increase the braking distance
if the roads are or has loose gravel, tyres are worn, brakes are worn
how does a car break
the brakes use friction to slow the car down
what does it mean for breaking distance increases
it means there’s less friction being created so the braking distance is increased
work done
work is done when when energy is transferred from one store to another over a distance
-> the amount of energy transferred depends on the size of the force and how far the object moves while the force is pushing it
work done word equation
work done (J) = force x distance moved in the direction of the force (m)
kinetic energy
the energy stored in a moving object
-> the amount of kinetic energy depends on the mass object and its velocity
kinetic energy word equation
kinetic energy (J) = 1/2 x mass (kg) x (speed) squared ((m/s)squared)
what happens to the kinetic energy when a vehicle stops
the kinetic energy is transferred to other energy stores by the braking force
crumple zone
the zone at the front of the car which absorbs impact energy during a collision so that the deceleration and force is less (less of an impact)
inertial mass
a measure of an object’s resistance to acceleration when a force is applied; it is determined by applying a force to an object and measuring the acceleration that results from that force.
inertial mass equation
force / acceleration
what’s the difference between inertial mass and gravitational mass
Inertial mass is measured by measuring an object’s resistance to changes in velocity; while gravitational mass describes the force on an object in a gravitational field.
what is the practical in investigating acceleration
- using trolleys to investigate the effects of mass and force having acceleration
- the force will be provided by mass hang on a string
what are action-reaction forces
- They a pair of forces acting on the two interactive objects
- two forces are always the same size and an opposite directions but always the same type of force (e.g. pulling forces, gravitational forces etc.)
equilibrium in physics
The state of balance between opposing forces of actual static (as in a body acted on by forces whose resultant is zero)
what’s the difference between action reaction forces and balance forces?
- Action reaction forces act on different objects
- Balanced forces all act on the same object
unit for momentum
kg m/s
air resistance
a frictional force that opposes the motion of objects moving quickly through the air; the force due to air resistance increases as the speed of a falling object increases.
inertia
measure of how difficult it is to change the object’s motion
Write the process to investigate acceleration (CORE PRACTICAL)
- Put ramp on a slight slope so trolley starts to move a constant velocity on its own
- keep the mask constant having all mass on the trolley and they’re moving one at a time onto the hanger attached to a string to the trolley
- Use light gates to measure the velocity of the car at the start the end of its journey
- Use the equation: a = V squared - U squared / 2 x distance
- Repeat and calculate the average
