Kinesiology 2241A/B Lecture Notes - Lecture 9: Table Tennis, Body Force, Resultant Force
30 Oct 2018
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Lecture- Visualizing Forces
What is Force?
● Physics definition
○ A force is an action that causes mass to be accelerated
● Common definition
○ A push or pull
○ A rub or pressure
○ A blow or impact
○ Gravity
● Interact with pressure and sheer
● Force is something that causes mass to be accelerated (how fast you are changing your
speed)
● Force is changing your acceleration
Isaac Newton’s 3 laws
● Objects(like the soccer ball) don't want to be accelerated because objects
possess inertia
○ Moving along in constant velocity makes you happy
● The force required to accelerated an object is proportional to its mass
○ f= m x a
○ F and a have a direction and they move in the same direction
○ Big acceleration= big force is applied
○ If a thing is massive= you will get little acceleration vs accelerating a ping pong
ball with same force= big acceleration
● If a force is applied to an object, object pushes back with the same force
○ Consequences of applying force
○ If you apply force to something, it will apply the force back at you
○ It's the law of action and reaction
○ Everything does cancel out but its in different body
○ If you accelerate something in one direction, it accelerates back in the other
direction
Mass and Acceleration
● Mass is not a vector, it is a scalar so it has only 1 property
● Mass has a magnitude measured in Kg
● Weight is a force
● Weight is the force with which gravity pulls on you
Mass, weight and Gravity
● The amount of matter that makes up an object is its mass
● This is measured in Kg
● Gravity pulls all object toward the center of the Earth with a force that has the magnitude
● F= m x G
Document Summary
A force is an action that causes mass to be accelerated. Force is something that causes mass to be accelerated (how fast you are changing your speed) Objects(like the soccer ball) don"t want to be accelerated because objects possess inertia. Moving along in constant velocity makes you happy. The force required to accelerated an object is proportional to its mass f= m x a. F and a have a direction and they move in the same direction. If a thing is massive= you will get little acceleration vs accelerating a ping pong ball with same force= big acceleration. If a force is applied to an object, object pushes back with the same force. If you apply force to something, it will apply the force back at you. Everything does cancel out but its in different body. If you accelerate something in one direction, it accelerates back in the other direction.
