Lecture 13
For a given mass, the bigger force leads to...
greater acceleration (larger change in velocity)
Example of point of application
Gymnast landing force on achilles; the body is designed to manage force in certain directions/some directions become problematic, leading to injury (knee, side to side motion)
3 rules to newtons first law
1. a body will have zero acceleration if no forces act on it 2. in the absence of a net force the state of motion of an object will remain the same 3. a stationary object will remain motionless and a body in motion will continue to move in a straight line with same speed if the net force acting on it is zero
What are important interpretations of F=ma?
1. cause (force) and effect (acceleration) relationship 2. acceleration is in the same direction as the net force 3. acceleration is directly proportional to the magnitude of the net force 4. to produce a given acceleration, it takes a larger force for a larger object
2 rules to mass
1. direct measure of a body's resistance to change in a LINEAR motion 2. a direct measure of an object's inertia with respect to LINEAR motion
What are the characteristics of a force?
1. magnitude 2. direction 3. point of application
Definitions of force
1. the effect of one body on another 2. a push or pull applied to an object 3. that needed to change the state of motion of an object 4. that which causes acceleration
T/F the concept of force is NOT fundamental to understanding of causes of motion
FALSE, the concept of force IS fundamental
Another name for Newtons first law
Law of Inertia
T/F mass is a direct measure of inertia
TRUE
What is inertia?
a property of a body to resist a change in its state of motion
What kinematic quantity allows us to measure changes in the state of motion of an object?
acceleration!
example of inertia
bag of groceries on the front seat and then step on brakes; it moves
Force to acceleration is _____ to _____
cause to effect
kinetics
concerned with causes of motion
Newtons first law
every body continues in its state of rest or of uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it
Higher mass requires...
higher force for the same effect
example of inertia (2)
if you are sitting, you are resisting the change of standing
How do we change an object's motion/change direction?
object's inertia must be "overcome" (passing zero)
When we have more mass, we have to alter.....
our point of application/leverage
What is mass?
quantity of matter of which a body is composed
Newtons second law
sum of force = mass x acceleration
Newtons second law
the change of motion is proportional to the motive force impressed and made in the direction of the right line in which that force is impressed
Newtons third law
to every action, there is always an opposed equal reaction; or the mutual actions of two bodies upon each other are always equal and directed to the contrary parts
How does point of application work within force?
where an object is being applied, changes it by area of leverage