43 terms

Conceptual Physics Chapter 4 Newton's Second Law of Motion

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Net Force
The combination of forces acting on an object.
Acceleration depends on what?
Net force
To increase the acceleration of an object, you must?
Increase the net force acting on it.
When it is said an object's acceleration is directly proportional to the net force acting on it, it is shown as
Acceleration ~ Net Force
~
Directly proportion to
Friction
Usually reduces the net force and the resulted acceleration.
What causes friction?
the irregularities in the surfaces in mutual contact (it also depends on the kinds of material and how much they are pressed together).
The direction of the friction force is
always in the direction that opposes motion.
An object sliding down an incline experiences
friction directed up the incline.
An object that slides to the right experiences
frictions toward the left.
If an object is to move at constant velocity, a force equal to
the opposing force of friction must be applied so that the two forces exactly cancel each other. The zero net force will result in a zero acceleration and constant velocity.
The friction of sliding an object is somewhat
less than the friction that builds up before the sliding of the object occurs.
Static Friction
The force between two objects that are at relative rest by virtue of contact that tends to oppose sliding.
Sliding Friction
Contact force that tends to slow down the motion produced by the rubbing together of the surface of a moving object with the material over which it slides.
Friction occurs in
fluids - liquids and gases.
When does fluid friction occur?
As an object pushes aside the fluid it is moving through.
Fluid friction depends on what?
Speed
What is a very common form of Fluid Friction?
Air Resistance or Air Drag
When does air resistance increase?
When speed increases
Inertia
An objects resistance to a change in its motion
Mass
How much matter an object has; the quantity of matter in an object; the measure of the inertia or sluggishness that an object exhibits in response to any effort made to start it/stop it/or change its state of motion in any way.
The greater the mass of an object, the great its
Inertia
Weight
Usually the force upon an object due to gravity.
Mass and weight are
directly proportional to each other.
The direct proportion of mass to weight tells us what?
If the mass of an object is doubled, its weight is doubled / if the mass is cut in half, the weight is cut in half
Mass is more
fundamental than weight.
If you are trying to tell if an object is heavier than another, what do you do?
You shake it back and forth, rather than pick it up. Which every of the two objects is more difficult to move from side to side is the heavier of the objects.
In the US how is the measure of matter commonly expressed?
In pounds
In the rest of the world, how is the measure of matter commonly expressed?
Kilogram ( 1 Kg = 2.2Lbs )
Newton
in metric units; equal to a little less than a quarter pound; 1 KG = 9.8 N
Volume
The quantity of space an object occupies.
Acceleration ~ 1/mass
For a given force, the acceleration produced is inversely proportional to the mass.
Inversely
Two values change in opposite ways ( i.e. if one value doubles, the other value halves )
Newton's Second Law of Motion
The acceleration of an object is directly proportional to the net force acting on the object, is the direction of the net force, and is inversely proportional to the mass of an object.
Acceleration ~ Net Force / Mass
Newton's Second Law of Motion
Acceleration = Net Force / Mass
This expression may be used when using consistent units.
a
acceleration
Fnet
net force
m
mass
Using a, Fnet, and m, what equation can be made?
a = Fnet / m
An object is accelerated in what direction?
the force acting on it.
Applied in the direction of the object's motion, what happens?
the force will increase the object's speed
The acceleration of an object is always in what direction?
The direction of the net force.
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