Topic 2 Mechanics Spec FULL Flashcards
What are the SUVAT equations? (Has a division)
s = (u + v)t / 2
What are the SUVAT equations? (begins with just V)
v = u + at
What are the SUVAT equations? (Has a squared in it)
s = ut + 0.5at²
What are the SUVAT equations? (Begins with a V²)
v² = u² + 2as
What are all the different equation rearrangements for the SUVAT equation V = U + AT?
U = V + AT A = (V - U) / T T = (V - U) / A
What are all the different equation rearrangements for the SUVAT equation S = UT + 0.5 A T²?
U = ( S - AT²) / 2T A = [2 ( S - UT )] / T² T = ([√ 2AS + U²] - U ) / A
What are all the different equation rearrangements for the SUVAT equation S = ( U + V ) T / 2
U = ( 2 S / T ) + V V = ( 2 S / T ) + U T = 2 S / ( U + V )
What are all the different equation rearrangements for the SUVAT equations V² = U² + 2 A S?
A = ( V² - U² ) / ( 2 S ) U = ( √ 2 A S - V² ) S = ( U² + V² ) / 2 A
What does a curved Displacement-Time mean?
Means the object is accelerating
What happens to the Displacement-Time Graph if the objects acceleration is increasing at a uniform rate?
The rate of change of the gradient will be constant
What does the Gradient of a Displacement-Time Graph give?
Gradient tells you the velocity
What is the definition of Velocity?
Change in displacement / Change in Time
What must the line of a displacement-time graph be if the velocity is constant?
Straight line upwards
How do you calculate the velocity of an object that is accelerating?
To find the instantaneous velocity at a certain point you need to draw a tangent to the curve at that point and find its gradient
How do you calculate the average velocity of a displacement-time graph?
Divide the final (change in) displacement by the final (change in) time.
A positive linear gradientshows us the….
acceleration of the object
A negative linear gradient showus the…
deceleration of the object
How do you calculate the Gradient of a Velocity-Time Graph?
Gradient = Change in velocity / Time Taken
What does a steeper gradient mean on a Velocity-Time Graph?
Greater the acceleration
What do straight linear gradients indicate on a Velocity-Time Graph?
Acceleration is constant OR uniform
What does the area underneath a Velocity-Time graph show us?
The DISPLACEMENT (also works for non-linear velocity-time graphs)
What does the Height of an Acceleration-Time Graph show?
Acceleration at that time
What does the area underneath an Acceleration-Time Graph show?
Gives the objects change in velocity
If a=0 then what is the velocity of the object?
It has a constant velocity
How do you calculate the change in velocity on an Acceleration-Time Graph?
Area under the graph = change in velocity
Split the area underneath the Acceleration-Time Graph into squares and triangles
Name 3 different SCALAR quantities.
Mass
Energy
Time
Remember as MET
Name 3 different types of VECTOR quantities.
Displacement
Acceleration
Force
Remember as DAF
What is a SCALAR?
A Scalar has magnitude but no direction
What is a VECTOR?
A Vector has both magnitude and direction
Vector Notation - What do you do when vectors are acting in the same direction?
Add the vectors together
Vector Notation - If the vectors are acting in opposite directions what do you do?
Take one direction as positive and another negative and add them together.
What is the overall effect of vectors acting called?
Resultant
How do you resolve perpendicular vectors?
The resultant vector is the diagonal
How do you resolve these Coplanar Vectors?
By resolving each one into their Vertical and Horizontal Components!
What happens to the horizontal part a projectile if they are shot out of a cannon?
Nothing if there is no air resistance it remains constant
How is the vertical part of the projectile affected when shot out of a cannon?
Accelerates due to gravity by 9.81ms-1
What to remember when drawing free body diagrams?
That forces are vector quantities so the arrow should show the size of the force and the direction
What do you do when you have forces that look like this?
- Deal with the forces as two seperate, independant forces, acting at right angles to each other
- Perpendicular forces have no effect on each other
- Use trigonometry to find the size of the force
What is Newtons 2nd Law?
Acceleration is proportional to the Force
F = ma
What has to be true if F = 0?
From F = ma we can see that a = 0, because of Newtons 1st Law no resultant force measn no acceleration.
the object could be at rest or at terminal Velocity
What is the Gravitational Field Strength Equation?
W = mg
g = W/m
What can Weight also be called?
Force, F
CORE PRACTICAL - Determine the acceleration of a free-falling object
- Set up equitpment in the diagram
- Measure the hieght from the bottom of the ball bearing to the trap door
- Flick the switch to start the timer and disconnect the elctromagnet, releasing the ball bearing
- The ball bearing falls knocking the trap door and breaking the circuit which stops the timer
- Repeat three times and take an average
- Use these results to find G using a graph
Why is this not an example of a Newton’s 3rd Law Pair?
- Two forces in a Newton pair always act on different objects
- But in this example the contact force of the earth is acting on the person, and the wieght is the force of gravity on the person. So they both act on the same object, the person
How to identify a Newton’s 3rd Law Pair?
- Has the same magnitude (size)
- Acts along the same line but in different directions
- Acts on a DIFFERENT object
- Acts for the same amount of time
- Is the same TYPE of force
What is Newton’s 3rd Law of motion?
If an object A exerts a force on an object B, then B exerts an equal but opposite force on A.
What is Momentum defined as?
p = mv
What is the principle of Conservation of Momentum?
Whenever objects interact, their total momentum in any direction remains constant, provded that no external force acts on the objects in that direction.
What is the equation that links momentum to Newton’s Laws of motion?
Force X Time = Change in momentum
What does the equation Force X Time = Change in momentum show us?
That the greater the force on an object and the longer it acts for, the greater the change in the objects momentum
What is an Impulse?
- Is the quantity ‘Force X Time’
- Measures the effect of a force
- Measured in Newton Seconds (Ns) which is the equivalent to the units of momentum (Kgms-1)
What is 1 kgms-1 equal to?
1 Ns
What is the Moment equation?
Moment of a Force (Nm) = Force (N) X Perpendicular distance from the axis of rotation (m)
What is the Principle of Moments?
For a body to be in equilibrium, the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point.
When dealing with an unusual moment what can we assume?
All the weight of the object acts through its centre of gravity
Apply the principle of moments to a body in equilibrium.
- If the centre of gravity is to one side of the pivot then the object will rotate anti-clockwise or clockwise depending on the side of the centre of gravity from the pivot
- If the centre of gravity is directly above the pivot , then there are no clockwise or anti-clockwise moments and so the broomsitck is in equilibrium
What is the Moment of a Force Equation?
Moment of a Force = Force X Perpendicular Distance
Measured in Nm
What is the Principle of Moments?
Sum of clockwise moments = sum of the anti-clockwise moments
What is the Centre of Gravity of an Object?
Is the point at which we can take its entire weight to act
What is an Objects centre of mass?
Is the point at which we can take its entire mass to be concentrated
What is the link between moments and the centre of gravity?
You presume the weight of the object acts through its centre of gravity which means it is the centre of the moment and perpendicular distances should be measured from that point.
What is the Work Done equation?
Work Done = Force X Distance in the direction of the force
Measured in J - Joules
How do you calculate the Work Done, when the force applied is at an angle?
1 - Need to split the force into its HORIZONTAL and VERTICAL components
2 - Consider what plane the force is acting in Horizontal or Vertical (is it moving along the ground if so you dont need to worry about the vertical component)!
3 - Use SOH CAH TOA to split the components up
What is the Kinetic Energy Equation?
KE = 0.5 x m x v*2
What is the Gravitational Potential Energy Equation?
ΔGPE = m x g x Δh
What is the Interaction of Kinetic Energy (KE) and Gravitational Potential Energy (GPE) when rolling a ball down a hill?
When the ball is at the top of the hill the ball contains mostly GPE but as it accelerates down the hill this energy is transferred into KE.
GPE Lost = KE Gained
Work Done = Energy Transferred
What are the two different Power equations?
P = E/t
P = W/t
What are the Efficiency Equations?
Efficiency = Useful Energy Output / Total Energy Input
Efficiency = Useful Power Output / Total Power Input
