Speed Distance & Mass Metric System – Physics
This chapter covers speed distance and mass metric system of physics.
What is forced expressed as in the metric system
To find the net result of two vectors we use the ___ rule
The process of determining the components of a vector is called
The tendency of objects to resist changes in motion
Is a measure of sluggishness of objects to resist changes in thEir motion
The metric system unit for this measurement of sluggishness
Mass, net force
The acceleration of an object is inversely proportional to the ___ of an
object and directly proportional to the ___ _____ acting on the object
When the net force acting on an object is the forc of gravity only the
acceleration of the object is
When an object falls through air, the net force is equal to th vector sum of
the force of gravity downward and the force of air resistance up ward. When
these forces are equal, objects falls at a ____ speed
The total number of forces existing in the universe at any one time must be
( even or odd)
the state of an object or system of objects for which any impressed forces
cancel to zero and no acceleration occurs
The type of equilibrium that exists when an object is not moving. Net force=
A form of equilibrium where opposing forces balance each other out, and the
system as a whole does not change.
D= (monster formula)
Newton’s First Law
The Law of Inertia
Newton’s Second Law
Fnet = ma
Newton’s Third Law
For every action force there is an equal and opposite reaction force
Forces that result from direct physical contact between objects
Forces that exist between objects in the absence of physical contact
Contact Force Examples
Friction force, Normal force, Tension force
Field Force Examples
Magnetic force, Gravity force, Electrical force
Tendency of an object to maintain its state of motion
The state of a car moving in constant velocity or at rest
The state of motion if a nonzero net force acting on the car
Acceleration is directly proportionate to this quantity
Acceleration is inversely proportionate to this quantity
Measure of the force of gravity on an object
Units used for the force of gravity of an object
measure of the quantity of matter of an object
Units used for the quantity of matter of an object
107,00 kilometers per hour
how we are moving relative to the sun
credited with being the first to measure speed by considering the distance
covered and the time it takes
defined as the distance covered per unit of time, how fast something moves
slash symbol (/)
is read as per and means divided by
is the speed at any instant
average speed equation
total distance covered/time interval
total distance covered equation
average speed x time
how fast an object is going and in what direction, we need to know both the
speed and the direction of an object for this
a quantity in physics that specifies a direction and a magnitude is called
means steady speed
means motion in a straight line at a constant speed
is how quickly velocity changes; the change in velocity, also is not just
the total change in velocity but also the time rate of change or the change per
second in velocity, and it applies to decreases as well as increases in
velocity (changes in both speed and direction
change in velocity/time interval
the key idea that defines acceleration
a large decrease per second in the velocity of a car
when we accelerate because our direction is changing
speed an velocity
are commonly used interchangeably when straight-line motion is being
acceleration equation (along a straight line)
change in speed/time interval
developed the concept of acceleration in his experiments on inclined planes,
and found greater accelerations for steeper inclines
velocity acquired equation
acceleration x time
instantaneous speed or velocity
are at any time simply equal to the acceleration multiplied by the number of
seconds it has been changing
no air resistance
all objects can fall with the same unchanging acceleration
when a falling object is free of all restraints- no friction, with the air
or otherwise- and falls under the influence of gravity alone, the object is in
free fall equation
during each second of fall, the object gains a speed of 10 meters per
second, and the gain per second is its acceleration
velocity acquired in free fall from rest equation
instantaneous speed is zero
at its highest point, when it is changing its direction of motion upward to
the object slows as it rises
during the upward part of this motion
downward velocities have this
distance traveled equation
1/2(acceleration x time x time), ?=1/2gt squared
is a common observation that many objects fall with
is the fact that is responsible for these different accelerations, it also
appreciably alters the motion of things like feathers
speed or velocity
is how we specify on how fast something is falling, and it is expressed as
a rate of a rate
is what makes acceleration so complex
if you jump higher than this than you are exceptional
no amount of leg or arm pumping or other bodily motion can change your hang
time when you are this
the jumpers horizontal speed remains constant while the vertical speed
described _____ to something
False: Speed is a measure of how fast something is moving
Speed is the
rate at which distance is covered, and it is measured in units of _____ divided
speed is the speed at any instant
False: Average speed is the total acceleration covered divided by the time
False: Velocity is speed together with direction
constant only when speed and _____ are both constant
the rate at which velocity is changing with respect to time
accelerates when its speed is _____, when its speed is ______, and/ or when its
direction is changing
False: Acceleration is measured in units of velocity divided by time
An object in
free fall has a constant acceleration of about ___m/s
systems giving context to numbers
(G or B), 10^9
a method of writing very large or very small numbers by using powers of ten;
0.0000000004 = 4x 10^-10 or
500,000,000,000,000 = 5 x 10^14
the number before the power of 10 in scientific notation, such as the number
5 in the scientific notation 5 x 10^14
Scientific Notation Multiplications
multiply the significands and then add the exponents;
(4 x 10^-10)(5 x 10^14) = 2 x 10^5
– multiplying 4 by 5 = 20 (converted to 2)
– adding -10 and 14 = 4
Scientific Notation Divisions
divide the significand in the numerator (top) by the significand in the
denominator (bottom) and then subtract the exponent in the denominator from the
exponent in the numerator;
(4 x 10^-10) / (5 x 10^14) = 8 x 10^-25
– dividing 4 by 5 = 0.8 (convert to 8)
– subtracting 14 from -10 = -24
Scientific Notation Raised to a Power
raise the significand to that power and then multiply the exponent by that
(6.0 x 10^4)^2 = 3.6 x 10^9
– squaring (^2) 6.0 = 36.0 (convert to 3.6)
– multiplying 4 by 2 (10^4 x 2) = 8
Scientific Notation Additions
exponents must always be the same (if not convert one), and then add the
3.7 x 10^4 + 1.5 x 10^3 = 3.9 x 10^4
– converting 1.5 x 10^3 = 0.15 x 10^4
– adding 3.7 and 0.15 = 3.85 (round to 3.9)
Scientific Notation Subtractions
exponents must always be the same (if not convert one), and then subtract
3.7 x 10^4 – 1.5 x 10^3 = 3.6 x 10^4
– converting 1.5 x 10^3 = 0.15 x 10^4
– subtracting 1.5 from 3.7 = 3.55 (round to 3.6)
= opposite / hypotenuse
= y / h
= adjacent / hypotenuse
= x / h
= opposite / adjacent
= y / x
the ratio relationship between the sides of right triangles
the power to which a base such as 10 (log) or “e” (ln) must be
raised to get the desired number;
– log 45 = X (10^x = 45), so X = 1.6532
– ln 45 = Y (e^y = 45), so Y = 3.8067
Natural Log (“e”)
“e” = ln = 2.71828
numbers that have both magnitude and direction, such as displacement,
velocity, acceleration, and force
numbers that have magnitude only, such as disctance, speed, energy,
pressure, and mass
the sum or difference of two or more vectors
X² + Y² = V² or, V = √X² + Y²
V = any vector (use V as the hypotenuse)
X = x component of vector V
Y = y component of vector V
branch of Newtonian mechanics that deals with the description of objects in
motion which allows us to describe an objects velocity, speed, acceleration,
and position with respect to time
an object in motions overall change in its position in space
a vector quantity whose magnitude is speed and whose direction is the
direction of motion;
v = displacement (x) / time (t)
SI units = meters/second (m/s)
average velocity (v, with a line over it) = Δx / Δt
the rate of actual distance traveled in a given unit of time:
s = distance (d) / time (t)
the average velocity as the change in time approaches zero;
v = limΔx / Δt
a vector quantity of the rate of change of velocity over time;
a = Δv / Δt
average acceleration (a, with a line over it) = Δv / Δt
the average acceleration as the change in time approaches zero;
a = limΔv / Δt
the objects velocity and acceleration are along the line of motion. The
pathway of the moving object is literally a straight line (one-dimensional
motion), but not limited to vertical or horizontal paths
Acceleration due to Gravity (g)
g = 9.8 m/s²
an object in motion who’s velocity is changing due to a constant force being
the five equations applied to objects in motion with constant acceleration;
v = v0 + at
x – x0 = v0t + (at² / 2)
v² = v0² + 2a(x – x0)
average v = (v0 + v) / 2
Δx = (average v)(t) = [(v0 + v) / 2] t
an object in motion that follows a path along two dimensions and the
velocity and acceleration are in two directions (usually horizontal and
vertical) and separate from each other
objects in linear motion experiencing acceleration equal to that of gravity,
discounting air resistance
the mass of an object multiplied by its velocity.
A moving object can have a large momentum if it has a large mass, a high speed,
It is harder to stop a large truck than a small car when both are moving at the
The truck has more momentum than the car. By momentum, we mean inertia in
momentum = mass × velocity
momentum = mv
When direction is not an important factor,
momentum = mass × speed
The quantity force × time interval is called impulse.
A force sustained for a long time produces more change in momentum than does
the same force applied briefly.
Both force and time are important in changing an object’s momentum.
When you push with the same force for twice the time, you impart twice the
impulse and produce twice the change in momentum.
Impulse Changes Momentum
The change in momentum depends on the force that acts and the length of time
If the momentum of an object changes, either the mass or the velocity or both
The greater the force acting on an object, the greater its change in velocity
and the greater its change in momentum.
A glass dish is more likely to survive if it is dropped on a carpet rather than
a sidewalk. The carpet has more “give.”
Since time is longer hitting the carpet than hitting the sidewalk, a smaller
The shorter time hitting the sidewalk results in a greater stopping force.
The safety net used by circus acrobats is a good example of how to achieve the
impulse needed for a safe landing.
The safety net reduces the stopping force on a fallen acrobat by substantially
increasing the time interval of the contact.
impulse = F × t
The greater the impulse exerted on something, the greater will be the change in
impulse = change in momentum
Ft = ∆(mv)
To increase the momentum of an object, apply the greatest force possible for
as long as possible.
A golfer teeing off and a baseball player trying for a home run do both of
these things when they swing as hard as possible and follow through with their
The force of impact on a golf ball varies throughout the duration of impact.
If you were in a car that was out of control and had to choose between
hitting a haystack or a concrete wall, you would choose the haystack.
Physics helps you to understand why hitting a soft object is entirely different
from hitting a hard one.
If the change in momentum occurs over a long time, the force of impact is
If the change in momentum occurs over a short time, the force of impact is
Cassy imparts a large impulse to the bricks in a short time and produces
considerable force. Her hand bounces back, yielding as much as twice the
impulse to the bricks.
The curved blades of the Pelton Wheel cause water to bounce and make a U-turn,
producing a large impulse that turns the wheel.
Conservation of Momentum
The momentum before firing a cannon is zero. After firing, the net momentum
is still zero because the momentum of the cannon is equal and opposite to the
momentum of the cannonball.
Law of Conservation of Momentum
Describes the momentum of a system
If a system undergoes changes wherein all forces are internal, the net momentum
of the system before and after the event is the same. Examples are:
atomic nuclei undergoing radioactive decay,
cars colliding, and
When a moving billiard ball collides head-on with a ball at rest, the first
ball comes to rest and the second ball moves away with a velocity equal to the
initial velocity of the first ball.
Momentum is transferred from the first ball to the second ball.
When objects collide without being permanently deformed and without generating
heat, the collision is an elastic collision.
Colliding objects bounce perfectly in perfect elastic collisions.
The sum of the momentum vectors is the same before and after each collision.
the constant velocity of a falling object when the force (net force = 0) of
air resistance is equal in magnitude and opposite in direction to the force of
What change in momentum does the cart undergo?
25 kg x m/s Change in momentum is equal to impulse.
If a the mass of the cart is 2 kg and the cart is initially at rest,
calculate its final speed.
5 kg·m/s divided by 2kg = 12.5 m/s
Momentum is equal to mass multiplied by velocity. The change in momentum is 25
kg·m/s and since it started at rest, then this is equal to its final momentum.
To get velocity we divide momentum by mass.
A 2-kg blob of putty at 3 m/s slams into a 2 kg blob of putty at rest
Calculate the speed of the two stuck-together blobs of putty immediately after
Momentum of the system before the
collision was 6 kg·m/s, and since momentum has to be conserved the momentum
after collision has to be 6 kg·m/s. The mass after
the collision is 4 kg, so the velocity after the collision is 1.5 m/s
Calculate the speed of the two blobs is the one at rest was 4 kg.
The momentum of the system before the collision was 6 kg·m/s, and since
momentum has to be conserved, the momentum after the collision has to be 6
kg·m/s. The total mass after the collision in this case would be 6 kg, making
the velocity 1 m/s.
When you ride a bicycle at full speed and the bike stops suddenly, why do
you have to push hard on the handlebars to keep from flying forward?
So that the reaction force of the handlebars on you will produce a
In terms of impulse and momentum, why are air bags in automobiles a good
In a crash you lose all momentum. Your change in momentum is equal to
impulse. Impulse is force multiplied by time. The air bag makes your collision
with the dashboard take longer so there is less force to hurt you.
Why is it difficult for a firefighter to hold a hose that ejects large
amounts of water at high speed?
The hose tends to recoil from the ejected water.
You can’t throw a raw egg against a wall without breaking it, but you can
throw it at the same speed into a sagging sheet without breaking it. Explain.
The sheet makes the collision take longer, and therefore there is a smaller
force on the egg. Remember that the impulse is equal to the change in momentum.
The change in momentum is defined by the mass and velocity, neither of which
are changed by how you stop the egg. So this means that the only way to
decrease the force on the egg is to increase the time it takes to change the
momentum, the sheet does this nicely.
Suppose you roll a bowling ball into a pillow and the ball stops. Now
suppose you roll it against a spring and it bounces back with an equal and
opposite momentum. Which object exerts a greater impulse, the pillow or the
The spring because the forward momentum is stopped and an equal and opposite
backward momentum is created, making the impulse twice as big because there is
twice as much change in momentum.
If the time it takes the pillow to stop the ball is the same as the time of
contact of the ball with the spring, how do the average forces on the ball
The force of the spring is twice as big. We know this because we found in
part a that the impulse is double. Impulse is time multiplied by force. If the
time is the same and the impulse is double that means that the force has to be
If you topple from your tree house, you’ll continuously gain momentum as you
fall to the ground below. Doesn’t this violate the law of conservation of
momentum? Defend your answer.
If the system is you and the Earth, then your momentum toward Earth is equal
and opposite to Earth’s momentum toward you. There is no net change in momentum
because while you’re falling down, Earth is falling (much less noticeably) up.
A bug and the windshield of a fast-moving car collide. Indicate whether each
of the following statements is true or false.
The forces of impact on the bug and on the car are the same size. True
The impulses on the bug and on the car are the same size. True
The changes in speed of the bug and of the car are the same. False the changes
of speed are very different due to the different masses and resulting
The changes in momentum of the bug and of the car are the same size. True,
since the impulses are of the same size.