Forces and Vectors
Cause accelerations - start, stop, speed up, slow down, change direction, or maintain the balance of an object
What are things forces do?
What do forces cause?
The force produced in resisting deformation perpendicular to the surface
What is the Perpendicular (Normal) Reaction Force?
The quantity of motion an object possesses, represented by the product of mass and velocity.
What is momentum?
L = m*v
The kinetics of particles, objects, or systems undergoing linear motion.
What is "Linear Kinetics"?
The gravitational forces exerted on a body that acts through the center of mass and towards the center of the Earth
What is weight force?
Fw = m*g
The type of surfaces and the strength of forces holding them together.
What are factors that influence friction?
The change in momentum overtime, which is dependent on the magnitude and duration of the net external force.
J = F * change in time
The natural tendency of a body to resist a change in its state of motion
What is Inertia?
Equal to the force required to accelerate a 1 Kg mass at 1m/s^2
What is 1 Newton?
The maximum amount of friction that develops just before two surfaces begin to slide.
What is Limiting Friction?
In the absence of net external forces, the total momentum of a system is constant
What is Conservation of Momentum?
The average location of the mass of an object
What is the Center of Mass?
(What is the Center of Gravity?)
For every action, there is an equal and opposite reaction, so that, when one body exerts a force on a second, the second body exerts a reaction force equal in magnitude and opposite in direction on the first body.
What is Newton's 3rd Law?
What is the Law of Action/Reaction
I am pulling a desk with a force of 99N at an angle of 40 degrees below the vertical y-axis. The desk weighs 234N. The floor is carpet and has a coefficient of friction of 0.27.
Draw a Free Body Diagram with all forces labeled.
A correct Free Body Diagram will include:
- The desk
- a vector at one of the top corners of the desk pointing upwards at an angle of 50 degrees
- friction force acting in the opposite direction to the pull (negative x-direction)
- the weight force acting straight down
- the reaction force acting straight up
Impulse due to the net force causes momentum to change
What is the Impulse-Momentum relationship?
True or False:
If more of an object is in contact with another object (ie. a greater surface area is shared), then the amount of dry friction will increase
False!
(Fx)2 + (Fy)2 = ?
(Fill in the missing piece of the equation, and provide the actual name of the term)
What is (Fres)2?
What is the Resultant Force? (Net Force)
You are pushing a desk with a force of 200 N oriented 25 degrees below the +x-axis. The desk weighs 115 N, and the coefficient of static friction between the desk and the floor is 0.36.
Solve for the net horizontal force and answer whether or not the desk moves?
Net horizontal force = 156.84 N
The desk does move!
You are practicing passing a soccer ball (0.45 kg) to your teammate. Your first pass had a contact time of 0.02 seconds and does not reach your teammate. Your second pass had a contact time of 0.07 seconds and does reach your team mate. If you kicked with the same force (280 N) both times, what was the difference in final velocity of the ball?
(Provide the final velocity for both kicks in your answer)
1st pass final velocity = 12.44m/s
2nd pass final velocity = 31.12 m/s
Difference: the ball is moving 31.12 m/s faster after the second kick than it is after the first kick
A push or pull that is exerted by an object on another object
What is a Force?