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Mechanics Term 1 By: Sonus, Steven, Steve, Kevin, ΣF=0, ΣF=m•a, Relates…
Mechanics Term 1 By:
Sonus, Steven, Steve, Kevin
Velocity and acceleration
Vector vs Scalar quantities
Acceleration
Rate of change of speed
Measured in m/s^2
Gradient of a velocity-time graph
Suvat Equations
Force and Motion in One Dimension
Newton's laws of motion
Newton's First Law of Motion
an object either remains at rest or continues to move at a constant velocity, unless it is acted upon by an external force.
Newton's Second Law of Motion
the rate of change of momentum of a body over time is directly proportional to the force applied and occurs in the same direction as the applied force.
Normal Forces
A contact force that is exerted perpendicular to an object when it is resting on a surface
When the normal force is greater than the downwards force, the object will get lifted off of the ground
Example: Lifts
When the normal force is equal to the downwards force, the object will remain vertically stationary
Example: Your body sitting on your chair
When the normal force is less than the downwards force, the object will sink
Example: A person in Quicksand
Horizontal & Vertical Forces
When ΣF=0, the object is eiither travelling at a constant speed or stationary
When ΣF<0, the object is decelerating
When ΣF>0, the object is accelerating
Calculating resultant forces
Direction
Calculated by using the tan inverse function
Magnitude
calculated using Pythagoras' Theorem
Forces and motion in 2 dimensions
Vector components
X-Components
Resultant vector components
Equation(find the magnitude of the resultant force)=> R^2 =
sqrt(X^2 + Y^2)
If resultant vector is positive
Object accelerates to the resultant angle(direction)
Equation (find the angle of resultant force)=> tanΘ = y/x
Resolving the vectors horizontally
Generally cosΘ + cosΘ...(it depends on the direction of the vector
Y-components
Resolving the vectors vertically
Generally sinΘ + sinΘ...(it depends on the direction of the vector
Weight
Resolving the weight parallel to the surface of a slope
Use WsinΘ (usually)(It depends)
Weight is directed downwards in rings
Normal contact force
On a slope Normal force < weight
On a flat surface(Not moving up or down) Normal force = Weight
Friction
F<=μR
F=μR
Limiting Equilibrium
F<μR
Equilibrium
Variables
μ = Coefficient of friction
R = normal contact force
F = Force
Smooth Surface
F=0R
ΣF=0
ΣF=m•a
Relates to the formula ΣF=m.a
Obtained by resolving and cancelling forces acting in opposite directions
Rough Surface
