Kinematics and Dynamics Flashcards
Vectors v. Scalars
- Vectors has magnitude ( number) and direction ( represented by arrow). Scalars are just magnitudes.
The vector can be bolded. - Vectors: Displacement, Velocity, acceleration, force.
- Scalars: distance, speed, energy, mass. Represented by italics.
Resultant
To find the result of the interaction between two vectors. Tip-to-tail method results in a greater vector and you add them. Vectors opposing ( opposite direction) each other you subtract them.
- The length of the vectors must be proportional to the magnitude.
We can also find the resultant by breaking vectors into individual components, how?
We find the resultant vector by finding the hypothenuse.
Displacement v. Distance
Displacement is a vector quantity and only considers the final and initial positions not the total distance it took to go from initial to final positions.
Distance is a scalar quantity and is concerned with the the total distance taken from the initial position to the final position.
Velocity
A vector quantity that describes the change in displacement over the change in time.
Speed
Speed is a scalar and describes the change in distance over time.
Instantaneous velocity
Describes the change in displacement over the change in time as time approaches zero.
Force
A vector quantity that is described as a push or pull on an object resulting in a change in velocity.
SI unit: Kg . m/ S^2
Gravitational force
The attraction force between two objects.
Fg= G(m1m2/d^2), where G is a constant and is 7x10^-11, m is mass of both objects, and d is distance.
What is friction and what are the 2 types?
Friction is a force between two objects that causes them to slow down or stop.
- Static friction (Fs) - friction between a stationary object and it’s surface.
Fs= ( coefficient of static) x ( normal force) - Kinetic friction ( Fk)- friction between a moving sliding object and it’s surface.
Fk= ( coefficient of kinetic friction) x (normal force).
Mass
Amount of matter in an object. SI unit is the kilogram.
Weight
The effect the gravitational force has on an object. SI unit is the newton.
What’s the equation that relates mass and gravitational force?
Fg=M x G
- Fg = gravitational force.
- Mass
- Gravitational force - 9.8
Center of mass
The point where the weight of the object is concentrated. This is where gravity acts on the object.
For symmetrical objects it’s at the center, for asymmetrical objects it can be anywhere.
Acceleration/ Deceleration
Instantaneous acceleration
Acceleration is the change in velocity over time. SI unit is m/s^2.
Deceleration is acceleration in the opposite direction.
Instantaneous acceleration is the exact same except with time approaches zero.
What are Newton’s 3 laws?
1st law ( Law of inertia) - An object at rest will stay at rest and an object in motion will stay in motion unless a force acts on it.
2nd law- When vectors add up it causes an object to acceleration and when they cancel out they don’t have an effect on the object. F=ma
3rd law - For every action there is an equal and opposite reaction.
Linear motion
When an object’s movement ( velocity and acceleration) is along a straight line.
What forces acts on free falling objects?
gravitational force ( value of -9.8).
If air resistance is not negligible than it acts like friction opposing the free fall. It increases as the velocity increases and is called the drag force.
The point where it’s falling at a constant velocity is referred to as terminal velocity. Happens because the drag force equals the weight of the object.
Projectile motion
Motion of an object that follows 2 dimensions and so acceleration and velocity are examined independently in the 2 directions.
The only 2 forces we consider in y direction is air resistance and gravity due to acceleration.
What are the forces acting on inclined planes?
The weight of the object ( mg) and the normal force.
Fgy = mgcos(theta)
Fgx= mgsin( theta)
** These are the weights of the objects in the y direction and x direction**
uniform circular motion
The centripetal force causes an object to move in a circular path.
- velocity vector is tangential to the centripetal force and always points in a straight line. So if the centripetal force stops, the object will move off in a straight line.
The tangential force ( force that points in the tangent position) is zero because there is no acceleration of the object.
Centripetal force (Fc) = MV^2/R
First condition of equilibrium
For an object to remain at rest all of the vectors acting on it must equal to zero.
Translational equilibrium
An object can be in translational equilibrium when the object is at rest or travels at the constant velocity in the same direction.
Rotational motion
An applied force at some distance away from the fulcrum provides torque so that arm rotates around the fulcrum.
The distance between fulcrum and applied force is the lever arm.
Torque = d ( lever arm) x F ( force)
If there is an angle between the applied force and the lever arm we multiply the above equation by sin theta.
Rotational equilibrium
When the vector forces acting on object cancels out causing not acceleration about the fulcrum.
Regarding rotational acceleration, forces that act clockwise are positive , negative? Counterclockwise?
Counterclockwise force will be positive..
Clockwise force will negative.
What happens to an object in motion when we suddenly remove the force acting on it?
It will move at a constant velocity.
Because acceleration will be zero therefore there will be no change in the velocity.
