Lecture 8: Visualizing Forces Flashcards
Force
Action that causes MASS TO BE ACCELERATED
Ex. push/pull, rub/pressure, blow/impact, gravity
Newton’s 1st Law
Objects don’t wnat to be accelerated b/c they possess INERTIA
- force must be applied to accelerate
- could want to remain at constant velocity
Newton’s 2nd Law
The force required to accelerate an object is proportional to its mass
F = m x a
Newton’s 3rd Law
If a force is applied to an object, the object pushes back with the SAME FORCE (RXN. FORCE)
- equally and oppositely directed force goes into object performing action
Action and rxn. force are NOT on the same object
Mass
Amount of matter that makes up an object
Measure in kg
Weight
Force that gravity pulls on the object with
Measured in Newtons
Mass and weight
Mass and weight are NOT the same thing
Weight involves gravity while mass does not
In space, mass is the same but weight is different b/c gravity is LESS
4 PROPERTIES OF A FORCE
Since force is a vector, it has 4 properties:
- Force has a MAGNITUDE measured in N
- Force has a DIRECTION
- Force has a POINT OF APPLICATION
- Force has a LINE OF ACTION
- where force is going + where it’s been
Centre of mass
aka centre of gravity
Gravity is applied at the centre of mass
does not have to be within the object and changes as you change position
can be useful to put centre of mass outside of body = high jump
Human centre of mass
Males: slightly above belly button (more shoulder-y)
Females: slightly below belly button (more hips)
Collinear forces
Lines of action are all parallel
Lifting, holding and dropping weights
If you need to lift, you need more force than gravity
To stay holding a weight, force = gravity
To drop a weight, force needs to be less than gravity
