Mechanincs Flashcards
What are scalars?
Something that has magnitude (size) but not direction
What are vectors?
Something that has magnitude and direction
What is resolving a vector?
Splitting a vector up into it’s horizontal and vertical components
How do you find its horizontal component?
horizontal component = hypontenous(resultent vector) * cosx
How do you find its vertical component?
vertical component = hypontenous(resultent vector) * sinx
What are the SUVAT equations?
v = u +at
s =(u+v)t /2
s=ut + (1/2)(at^2)
v^2 = u^2 +2aS
What is “g”?
The acceleration due to gravity @ 9.81ms^-2
It can be used to replace “a”in SUVAT equations but should using be a negative number due to it acting downwards
How do you calculate g?
Set up using
an electromagnet with a switch
a steel ball
trapdoor
Timer
computer
Measure the distance between the ball and the trapdoor
Flick the switch to make the steel ball fall
Make the switch also start the timer
Steel ball hits the trap door breaking the circuit and stopping the timer
Record the t
Repeat changing the height for 3 times
Use the rests to plot a graph for height against t^2
The gradient is the acceleration
How would you reduce the uncertainty?
Use a computer to automatically drop the ball and start the timer
Have height to decrease the uncertainty
Why do objects in projectile motion curve?
The horizontal and vertical motion must be thought of separately. Horizontal motion stays constant while vertical motion is affected by g
What is a free-body force diagram?
Diagram that shows all forces acting on a single body
What is newton’s first law?
The velocity of a object will stay constant (will not change) unless a resultant force acts on it.
What is newton’s second law?
F = ma The acceleration is proportional to the force acting upon the object.
What is newton’s 3rd law?
Every force has an equal and opposite reaction
If an object A exerts a force on an object B then object B exerts and equal but opposite force on object A
What is fluid friction?
A.k.a drag
It increases with viscosity
It increases with the speed
it increases with surface area
What is terminal velocity?
When the resultant force of an object is 0 due to frictional drag and the driving force is in equilibrium
Terminal velocity (big mark question pls)?
An object accelerates from rest (either due to weight or driving force ect)
—-> increase in velocity
——->increase in the frictional forces
———–>reduction in resultant force
——————>resultant force of an object is 0 due to frictional drag and the driving force is in equilibrium
What is momentum?
p = mv
What is the main property of momentum?
Momentum is always conserved if no external forces are acting upon it
How would you investigate momentum?
Air track (reduces friction) and light gates
Trolleys are pushed into each other
Light gates measure velocity of trolleys after they pass through them
Using the initial and final velocity you can find out the initial and final momentum of the trolleys
What links force to momentum
f = ma
p = mv
——-> F = change in p/ change in t
What is work done?
Force x parallel to the force Distance
What do you do if the force is not parallel to the direction of motion?
Resolve the force and use the component that is parallel to the force
What is power?
P = work done / time
What is the principle of conservation of energy?
Energy cannot be created or destroyed, only transferred from one form to another
What is efficiency?
useful energy output / total energy output
What is the centre of gravity?
The single point in which it is considered that all the weight of an object acts through
How does the centre of gravity relate to the stability of an object
The lower the centre of gravity the more stable the object would be.
Bigger base leads to more stability
What is a moment?
moment = force * perpendicular distance from the line of action
What assumption is made when using SUVAT?
Force and acceleration is constant
What are the requirements for Newton’s 3rd law pairs?
The forces must be of the same type and equal magnitude
I push on wall and wall pushes on me (YES)
Gravity pulls on the book and the table pushes on the book (NO! different type of force)
