Date post: | 25-May-2015 |
Category: |
Documents |
Upload: | maria-donohue |
View: | 1,615 times |
Download: | 0 times |
Relative Velocity and Frame of Reference
Frame of Reference
Motion is a change in position relative to a frame of reference
Frame of reference: a set of objects used to measure a change in position.1. Standing frame of reference2. Moving frame of reference.
Speed vs Velocity
Speed is the distance an object travels in a time period.▪ S = d/ t ▪ Units m/s
Velocity of an object is the speed and direction of motion. Ex: A car travels 60 m/s north on I-75 and then
turns around and goes south at 60 m/s. Does the car have the same speed? Same velocity?
Ans: Same speed, different velocities b/c different directions
Relative Speed/ Velocity
Relative speed and velocity depend on a frame of reference.1. Standing frame of reference
a. Objects moving in the same directions, add (+) speeds
b. Objects moving in opposite directions, subtract (-) speeds
Relative Speed/ Velocity
1. Moving frame of referencea. Objects moving in the same directions,
subtract (-) speedsb. Objects moving in opposite directions, add
(+) speeds
Calculating Relative Speed Flowchart
What is the frame of
reference?
Standing
Same direction
“+”
Opposite directions
“−”
Moving
Same direction
“−”
Opposite directions
“+”
Newton’s Gravitational Force
Force of Gravity
Gravitational force – attractive force that any two objects having a mass exert on each other. On Earth, gravitational force is equal to
the mass of the object times the gravitational constant (accelaration)▪ F = mg▪ Units = kg m/s2 newtons (N)▪ Earth average g= 9.81 m/s2
▪ Gravitational force = weight
Review
Mass vs. Weight Mass – amount of matter in an object▪ Units = kilogram (kg)
Weight- how heavy something is. ( gravity applied on the mass of an object) ▪ Units = Newton (N) ▪ Newton is a derived unit (kg m/s2 )
Universal Law of Gravitation Universal Law of Gravitation(ULG) – used
to describe attractive force between large objects such as the planets and the sun.
G has constant value of 6.67 x 10-11 N m2/kg2
m1 = mass of object 1
m2 = mass of object 2 d = distance between two objects
Using the ULG
Ex: A satellite orbits Earth at a distance of 72 km. If the satellite were to orbit Earth at a distance of 144km away from the center of the Earth, by how much would the force between the satellite and the Earth change.a. The force would be 4 times greaterb. The force would be 2 times greaterc. The force would be 2 times smallerd. The force would be 4 times smaller
Using the ULG
Solution:
Proportions
Proportions are relationships between two or more things.
To find relationships divide (÷)or create a ratio (fraction)
Direct relationships are shown as follows X = Y If x increases, y increases
Inverse relationships X = 1/Y If Y increases, X decreases
Using the ULG
Ex2: Two one kg spheres are 1 meter apart. Which of the following would double the gravitational force between them?a. Doubling the mass of one sphereb. Doubling the mass of both spheresc. Halving the distance between both
spheresd. Doubling the distance between both
spheres
ULG
Ex3: Two 20 kg spheres are 15 meters apart. Which of the following will give a gravitational force that is ¾ of the original force?a. Double both masses, leave the distance the
same.b. Triple one mass, double the distance between
themc. Triple both masses, double the distance between
themd. Double both masses, double the distance
between them.
Energy
Types of Energies
Radiant Energy- energy from the sun in the form of electromagnetic waves (light)
Electrical Energy – energy of flowing electric particles, current.
Heat Energy – energy transferred by a difference in temperature
Chemical Energy – energy given off by chemical reactions
Types of Energies
Kinetic Energy – energy that an object has due to its motion KE = ½ mv2
Units = kg m2/s2 Joules (J)
Potential Energy – stored energy that an object has due to its position PE = mgh Units = kg m/s2 m Joules (J)
Types of Energies
Mechanical energy – energy used to perform work
Practice
Energy Transformations
During phase changes, energy is either absorbed or released.
Energy Flow & Transformation Energy from the sun is captured by the green plants, (trophic level I)transformedinto chemical energy through photosynthesis and passed on through the various trophic levels.
The flow of energy is unidirectional i.e., non-cyclic.
Some energy is lost in theform of heat at every statein the atmosphere. Energy pyramid
9. Buzz Lightyear is on a mission to save his home planet Galactika. A giant blazing meteor with a mass of 2.5 x 10^8 kg is creeping dangerously close to Galactika, whose mass is of 5.56 x 10^23 kg. It is currently at a distance of 6.99 x 10^3 km from his planet. Woody helped Buzz create the Mega Meteor Blaster to save Galactika. If Buzz uses the blaster on the meteor it will decrease the mass of the meteor by 4 but also push the meteor closer to the planet, cutting the distance between Galactika and the meteor in half. Time is ticking and Buzz needs your help to decide if he should use the Mega Meteor Blaster. Should he use the Blaster and what would happened to the force between Galactika and the meteor if he did?