Chapter 4 Flashcards
acceleration
the rate of change in velocity; the change in velocity over change in time; the SI unit for acceleration are m/s2, meters per second squared or meters per second per second; how fast the velocity is changing; vf - vo / t. E.g. Truck goes 0-60mph in 30 seconds; 60/30= 2 miles per hour per second
average velocity
displacement / time
(speed is associated with distance; displacement is associated with velocity)
Newton’s First Law
Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon. I.e. object in motion stays in motion unless a force is acted upon it.
Newton’s Second Law
The alteration of motion is ever proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed;
Acceleration is directly proportional to…
Net external force
Acceleration is exactly inversely proportional to
Mass
Acceleration of an object depends ONLY on
Net external force and mass of the object
In equation form, Newton’s Second Law:
Net Force = ma
F = ma is used to define the force in terms of…
Three basic units for mass, length and time
SI unit of force is called the
Newton (N)
1N =
1 kg x m/s 2 (note: mass, length and time)
Mass and acceleration are…
Inversely proportional to each other
Newton’s Third Law
Forces are equal and opposite
Combining Second and Third
Because forces are equal and opposite (third law), if an object with a larger mass pushes against an object with a smaller mass, the acceleration of the object with the smaller mass has to increase to keep the equation balanced. The equation for the Second Law is Net Force = mass x acceleration. (In car collision example, the smaller car’s acceleration increases with the collision to keep the equation balanced, thereby making the collision worse for the smaller car.)
Newton’s Laws of Motion describe how…
forces cause changes in motion
A force is a…
Push or pull on an object
A force is a [blank] quantity meaning…
Vector quantity. It has both magnitude and direction
Force is measured in _________
Newtons
Net Force is
vector sum of all the forces acting on an object
If two forces act in opposite directions…
One can be considered negative and the other positive
Free body diagram
Has a central point, or square, representing the object experiencing the force(s), as well as arrows representing each force acting on the object.