PHYSICS P5: FORCES Flashcards
what is the limit of proportionality in a graph?
it is where Hooke’s Law begins to break down due to the five applied to the spring
HOOKE’S LAW KEY EQUATION:
F = ke
F - force (measured in newtons)
k - spring constant (measured in N/m)
e - spring extension (measured in M)
what should Hooke’s Law be thought as?
it should be thought as the stiffness of a spring
KEY EQUATION FOR SPRING EXTENSION:
force applied
——————— = spring extension
spring constant
Hooke’s Law Required Practical Steps:
-set up ruler next to spring being weighed down by a stack of newtons
-measure the original length of the spring
-hang different masses and measure spring in each case
-adding masses increases downward force
-extension of spring = length with masses - original length
-plot a graph with extension on the x axis and force on the y axis
what is being put on the x and y axes on the RP graph?
x axis - extension of spring
y axis - the force applied
EQUATION FOR SPRING EXTENSION:
spring extension = length of loaded spring - natural length of spring
what are contact forces?
they happen when two objects are physically touching.
examples include air resistance, tension, friction, and normal contact force
what are non contact forces?
they happen when objects are separated or not touching.
examples include electrostatic force, gravitational force, and magnetic force
what is an interaction pair?
a set of 2 forces that are equal and opposite, acting on 2 interacting objects
what is tension and friction?
-tension is the pulling force that a string/cable exerts when something pulls it
-friction is whenever two surfaces are touching and try to move against each other
what is a normal contact force and air resistance?
-a normal contact force is when an object at rest exerts a force on the surface
-air resistance comes about when an object moves through air and collides with air molecules, creating a force that slows the object
what axis does the information go on for a distance/speed - time graph?
y axis - distance
x axis - time
what does it mean if there is a straight line on the graph?
there was no movement for the selected period of time
COMPLETE QUESTION:
if an object travels at 15 metres in 5 seconds, what is the slope of its graph?
3m/s
what does a positive and negative gradient mean?
-a positive gradient shows an increase in speed
-a negative gradient shows a decrease in speed
what is thinking distance?
the distance travelled between when the driver realised they need to brake and when they apply the brakes
what is braking distance?
the distance the car travels between the driver applying the brakes and the car stopping
how do you calculate stopping distance?
thinking distance + braking distance
what are the factors that might will affect thinking distance?
-distractions will cause a driver to react slower in emergencies
-tiredness will also slower a driver’s reaction
-drugs or alcohol will definitely reduce a driver’s reaction
what are some factors that will affect braking distance?
-road conditions will increase braking distance if they are wet or icy
-car’s condition as the tyres might be in poor condition
-initial car speed as it has to travel further before it will come to a stop
what’s the acceleration of any falling object near earth?
9.8 m/s squared
what are the three stages of falling?
-object accelerates downward because of gravity
-as speed increases, frictional forces like air resistance increase
-at terminal velocity, an object’s weight is balanced and the resultant force is 0
what is Newton’s first law?
it states that an object will remain in the same state of motion unless a resultant force acts on it. if the resultant force is 0 this means:
-a stationary object stays stationary
- a moving object continues to move at the same velocity
what is Newton’s second law?
it can be described through this equation:
F = m a
F - force - measured in newtons (N)
m - mass - measured in kilograms (kg)
a - acceleration - measure in m/s squared
what is Newton’s third law?
whenever two objects interact, they exert equal and opposite forces on each other
