Science: Final Flashcards
Section 1: Pressure
….
Pressure
the force pushing on a surface
Pressure formula
Force/Area
Pressure unit
N/cm^2
Pascal
Newton per square meter
Archimedes’ Principle
A submerged object displaces, or takes the place of a volume of fluid equal to it’s own value.
Archimedes’ Principle in relationship to the buoyant force…
Buoyant force= weight of the displaced fluid
Q: If the buoyant force on an object in water is equal to the object’s weight the object will….
float
Q: At higher elevations, air pressure is…
less because there is less air above
Q: The buoyant force…
acts upward against the force of gravity
Q: As depth increases, water pressure…
increases
Q: When would you exert less pressure on the floor? When your entire body is lying down on the floor, or when you are standing up. Why?
When your entire body is lying down on the floor because you exert a large mass on a larger area, spreading out your body’s mass and therefore exerting less pressure.
Q: You have a closed bottle of soda . The force on the bottle cap due to the carbonation of the soda is 45 N. If the area of the bottle cap is 15 cm^2, what is the pressure on the cap? (Show work)
(Use formula)
45/15 = 3 N/cm^2
Q: You suspend a pencil sharpener from a spring scale. It’s weight is 20.00 N. Next, you immerse the pencil sharpener in a tank of water. The pencil sharpener appears to weigh 17.5 N. What is the buoyant force acting on the pencil sharpener? Does it sink or float? Why? (Show work?
(Formula = normal weight - submerged weight)
20 - 17.5 = 2.5 N
The pencil sharpener sinks because the buoyant force is less than the object’s weight.
Q: An empty soda can is left on a table. The can is closed and surrounding room pressure is normal. Compare the pressure inside the can to the pressure outside the can. Explain your reasoning.
The pressure inside the can is greater to the pressure outside the can. The force is unequal because the pressure is acting in all directions, but only inside the can. This will cause the can to explode.
Q: Explain why you seem to weigh more on land than in water
You seem lighter in water because the buoyant force is pushing up against gravity. On land there is no buoyant force.
Q: Atmospheric pressure is the pressure exerted by the weight of air in the atmosphere of Earth. It is approximately 14.7 psi. Explain why we do not feel this pressure.
We don’t feel this pressure because the fluids inside out bodies balance the pressure outside.
Section 2: Temperature and Thermal Energy
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Temperature
Measure of the average kinetic energy of the individual particles in an object.
Thermal Energy
Total internal energy of a substances particles due to their movement. Depends on substances temperature, number of particles in amount, and particle arrangement.
Conductor
Material/substance that transfers thermal energy easily
Insulator
Material/substance that does not transfer thermal energy easily
Convection
Up and down movement of fluids caused by heat transfer.
Convection Current
The heating, cooling, expanding, and contracting process of fluids transferring heat.
heated = becomes less dense and rises
cooled = becomes more dense and sinks
The stages on a changes of state chart
solid, freezing/melting, liquid, condensation/vaporization, gas
Q: The process by which heat is transferred from one particle of matter to another without the movement of matter itself is called…
conduction
Q: In which direction does heat move?
higher temperature to lower
Q: Which method of heat transference does not require matter to transfer thermal energy
radiation
Q: Heat is a transfer of
thermal energy
Q: 42 degrees Fahrenheit is how many degrees Celcius?
5.556
Q: 95 degrees Celcius is how many Kelvins?
368.15
Q: When you heat a pot of water on the stove, a convection current is formed. Explain how this convection current forms. Include in your answer what happens to the water near the heat source, water not near the heat source, and how this affects the waters density.
The water near the heat source will become hotter, and less dense. This will cause it to rise up. The water farther from the heat source will be more cool, more dense, and sink. This cycle will continue as the more dense water that has lowered becomes less dense, and the water that has risen cools and becomes more dense.
Q: On a cold winter day would you rather wear a coat made of fabric or aluminum foil? Explain your choice using what you know about the properties of conductors, insulators, and heat transfer.
On a cold winter day I would rather wear a coat made of fabric because aluminum foil is a conductor, not an insulator. That means aluminum foil will not contain your body heat well, and you’ll be very cold. Fabric, on the other hand, is an excellent insulator because it keeps your body heat contained, and you’ll be generally warm on a cold winter day.
Q: In one mug you have 470 mL of hot coffee. In another mug you have 470 mL of iced coffee. Which drink has particles with greater average kinetic energy?
The hot coffee has particles with a greater average kinetic energy because it is warmer and less dense, meaning the movement of the particles will be greater. Therefore, the hot coffee will have a greater kinetic energy than the iced coffee.
Q: Which has the highest amount of thermal energy- a glass of 200g liquid with a temperature of 30 degrees Celcius or a glass of 300g liquid with a temperature of 60 degrees Celcius.
The second glass will have the highest amount of thermal energy because it is warmer, meaning less dense with more movement. It is also containing a greater mass. Therefore, there is more of it.
Section 3: Forces
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Force
push or pull on an object resulting from the object’s interaction with another object. Forces have both SIZE & DIRECTION
Balanced Forces
Equal forces acting on one object in opposite directions. (DON’T CHANGE CURRENT STATE OF MOTION)
Unbalanced Forces
Cause an object to start moving, stop moving, or change directions (accelerate)
Net Force
Sum (overall) force acting on an object (same direction is + and different directions is -)
Gravity
attractive force which pulls two objects toward each other. The strength of the gravitational force between two objects depends on two factors, MASS & DISTANCE
Air resistance
Fluid Friction resulting from the object’s leading surface and air molecules. The amount of resistance depends on:
- speed of object
- amount of surface area
Terminal Velocity
Moment at which air resistance equals to the force of gravity. Object reaches it’s greatest velocity. (Net Force 0)
Newton’s First Law of Motion
(Inertia) An object at rest will stay at rest, and an object in motion will stay in motion at a constant velocity unless acted upon by an unbalanced force.
Newton’s Second Law of Motion
(F = M/A) When a constant force acts on a massive body, it causes it to accelerate at a constant velocity
Newton’s Third Law of Motion
For every action there is an equal and opposite reaction
Momentum
Quantity of motion (mass x velocity)
Q: Action and reaction forces don’t cancel each other out because the forces act…
on different objects
Q: An object in “free-fall” only has the force of _____ acting upon it.
gravity
Q: Friction acts in the direction _______ to the applied force.
opposite to
Q: Explain how rockets are launched into space…
Newton’s Third Law of Motion
Q: Why heavier objects require more force than lighter objects to move or accelerate them.
Newton’s Second Law of Motion
Q: While riding on a skateboard you fly forward off the skateboard after hitting a rock.
Newton’s First Law of Motion
Q: At what rate on Earth does an object in FREE-FALL accelerate?
9.8 m/s^2
Section 4: Energy
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Energy
Ability to do “work” or cause change
“Work”
product of FORCE + DISTANCE when a force is used to move an object
Joule
Unit of work and energy
Potential Energy
Stored energy of position possessed by an object (“held in readiness”)
mass x 9.8 x height
Kinetic Energy
Energy of Motion
Formula: mass x velocity^2 / 2
Law of Conservation of Energy
Energy cannot be created or destroyed
Forms of Potential Energy
Chemical, Nuclear, Stored Mechanical, Gravitational, etc.
Forms of Kinetic Energy
Radiant. Thermal, Motion, Sound, Electrical, etc.
Section 5: Motion
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Motion
State in which one object’s distance from another is changing
Reference Point
Place or object used for comparison (position).
Velocity
Speed with direction OR rate of change of position
Acceleration
Rate at which velocity changes (a change in speed or direction)
Formula: Final velocity - Initial velocity / Time
Graph of distance and time for acceleration and constant speed
Acceleration: curves
Constant: Linear
Graph of velocity and time for acceleration and constant speed
Acceleration: Linear
Constant: Horizontal
Q: A “merry-go-ride” at a carnival is constantly accelerating because it is…
always changing directions
Average Speed Formula
Initial + Final / 2
Speed Formula
distance / time
Velocity Formula
acceleration x time
Acceleration Formula
force / mass
Q: A car moving with a constant velocity is a car with zero acceleration
True
