Force and motion Flashcards
Acceleration
Is the rate of change of velocity per unit time (vector quantity
Displacement
the change in position of an object (vector quantity
Distance
the total length of a given path between two points (scalar quantity)
scalar quantity
Is a quantity that has only magnitude (size)
Speed
the rate of change of distance per unit time (scalar quantity
Vector quantity
a quantity that has magnitude (size) and direction
Velocity
the rate of change of displacement per unit time (vector quantity
Velocity conversions. ms –> kmh
To convert from m s-1 to km h-1, multiply by 3.6. To convert from km h-1 to m s,-1 divide by 3.6.
Average velocity formula
v = Δs/ Δt = s2 − s1/ t2 − t1
v = average velocity (m s−1), s = displacement (m), t = time (s)
Instantaneous velocity
Instantaneous velocity describes the velocity at an instant in time. The instantaneous velocity can be calculated using the formula for average velocity if the velocity is constant. Instantaneous speed is always equal to the magnitude of the instantaneous velocity.
Acceleration formula
a = Δv /Δt = v − u/ t2 − t1
a = acceleration (ms-2), v = final velocity (ms-1), u = initial velocity (ms-1), t = time (s)
Constant acceleration equations
Equilibrium
the state of having all the forces acting on an object in balance which means the net force on the object is zero
Force
a push or a pull with an associated magnitude and direction (vector quantity)
gravitational force
the force experienced by an object due to the gravitational field of another object
net force
the vector sum of all forces acting on an object
Newton’s first law
law that states an object will accelerate only if a non-zero net force (unbalanced force) acts upon it
Newton’s second law
law that states the acceleration of an object is equal to the net force applied divided by the mass of the object being accelerated
Connected bodies
Two or more objects in direct contact or attached such as through a rope of cable.
Newton’s third law
law that states that for every force there is a reaction force of equal magnitude and opposite direction
normal force
the contact force that acts between two objects with the equal magnitude on each object and at right angles to the contact surfaces
Friction
a force that resists the relative motion of two surfaces which are in contact
Inclined Plane
A flat surface that is at an angle to the horizontal plane.
Tension
a pulling force between two connected bodies, the magnitude of both bodies is the same
What are two forces that always act on an inclined plane?
How is net force calculated?
When all the forces are added together it will result with the net (overall) force.
Formula for inclined planes
Fds=mgsin(θ)
Show the force due to gravity being resolved into two perpendicular and parallel.
When analyzing the whole system for connected bodies what should be analyzed?
When viewing connected bodies as a single system the tension forces should be ignored as they will have the same magnitude in opposite directions, therefore, canceling them out. The total mass should be used to address the system.
When analyzing a single object in a system what should be analyzed?
For a single object within a system only consider the forces directly acting on that object including tension force and only use the mass of that object.
What are the equations for the whole system and single parts that are connected bodies in tension?
Formulas for connected bodies in contact
Centripetal force
the net force causing circular motion which is always directed towards the center of a body circular path.
Frequency
the number of cycles completed per unit of time
period
time taken to complete one cycle
How can ciruclar speed be calculated and therefore what is its given formula?
The speed of a body can be calculated through distance over time. Distance around a full circle is the circumference (C=2πr) and the time taken for one revolution is T=1/f.
This gives v=2πr/T
v = circular speed (m s−1), r = path radius (m), T = period (s)
Centripetal acceleration
Vector quantity that measures the rate of change of instantaneous velocity when a body travels in a circular path.
Formula for centripetal acceleration
Why are objects undergoing circular motion accelerating despite having a constant speed?
Because the velocity of the body must be changing since its direction is changing.
What is the formula for Centripetal force through substitution of centripetal acceleration and Newton 2nd law?
conical pendulum
a mass on the end of a string which undergoes horizontal circular motion
Design Speed
The speed on a banked track for which there is no sideways frictional force acting on the vehicle
What three forces are experienced on banked tracks
- The force due to gravity (Fg)
- A normal force (Fn)
- A sideways frictional force (Not applicible in VCE physics)
The formulas for banked circular motion with trigonometry and Pythagoras theory.
What does the Design Speed formula show?
That as the slope increases the design speed increases and as the radius of the circular path increases the design speed increases.
Design Speed formula
Concial pendulums and its formulas
In vertical circular motion what direction does the normal force act on the object?
The direction of the normal force will always act on the object away from the track and the force due to gravity always acts downwards.
In VCE physics, regarding vertical motion what scenarios must be considered and what formula is used for those scenarios?
Forces at the top and outside of vertical circles what direction does the normal and net force act?
The normal force acts upward and the net force acts downwards towards the center of the circle.
The net force = Fg-Fn
Forces at the top and inside of vertical circles what direction is the normal and net force?
the normal/tension force acts downwards and the net force also acts downwards.
The net force = Fg+Fn or Fg+T depending if a string or cable is involved.
Forces at the bottom and inside of vertical circles what direction does the normal and net force act?
the normal/tension force acts upwards likewise with the net force meaning the net force is equal to Fn-Fg or T-Fg
when the normal force is zero at the top of a circle in vertical motion what is the relationship occurring and what does this mean for the overall velocity?
The relationship shows the formula v=√gr which then for an object on top of a circle will reach its maximum velocity and an object at the top inside of the circle will reach its minimum velocity.
Define projectile motion
motion of an object thrown or projected into the air, subject to only the acceleration of gravity.
