Lesson 4 Flashcards
Define speed.
Speed is the rate at which an object moves (ex. 100 km/h)
Define velocity.
The speed travelled in a given direction (ex. 100 km/h due east)
Define acceleration.
It is the change in velocity (ex. 9.8 m/s^2 downward)
What did the Copernican revolution spark for sir Isaac Newton?
The discovery of the laws of motion and gravity
Do all falling objects accelerate at the same rate?
Yes; everything on earth accelerates at 9.8m/s
- this means that if a falling object takes 1 second to reach the ground, it was falling at 9.8m/s, it it took 2 seconds, it was falling at 9.8m/s x 2, etc
What does net force change?
It changes the momentum of an object (which generally means acceleration, i.e. velocity)
What is a force?
it is a vector quantity (its direction matters)
- multiple forces can be applied to an object in different directions
What is weight? What is mass? Are they the same thing?
Weight = the force that acts upon an object (mass x gravity)
Mass = the amount of matter an object has
Weight does not equal mass
What is momentum?
mass x velocity
How can weight change?
In the amount of gravity that is acting on an object and the motion of the object (particularly acceleration)
- ex. a 100kg object on earth moving downward will be 100kg on the moon if it is moving upwards
What is angular momentum?
The rotational momentum of a spinning object
What is net force?
The direction an object will go when all other forces are also applied (like a tug of war between a strong guy and a 5 year old)
What is weightless free fall?
When the effects of acceleration are more powerful than the effects of gravity
What does the law of conservation state?
a quantity cannot be created or destroyed, it can only be exchanged for something else
What does acceleration upwards cause?
More gravity therefore more weight
What does acceleration downwards cause?
Less gravity therefore less weight
What were Newton’s Laws of Motion? (3)
- an object moves at a constant velocity unless a net force acts to change its speed or direction
- Force = mass x acceleration
- for every force, there is always an equal and opposite reaction force
What are the three laws of conservation? (3)
- Law of Conservation of momentum:
- the total momentum of interacting objects cannot change unless an external force is acting on them - Law of Conservation of angular momentum:
- angular momentum = mass x velocity x radius of angular movement
- as radius decreases, velocity increases and as radius increases, velocity decreases - Law of Conservation of energy:
- energy is conserved but can be exchanged with objects and with other forms of energy
- the total amount of energy of the universe was determined in the big bang and remains the same
What are the three basic categories of energy?
- kinetic energy (movement)
- radiative energy (light and gravity)
- potential energy (stored energy like electricity)
What are the 4 types of forces?
- gravitational
- electromagnetic
- weak
- strong
- these forces interact to create different kinds of energies
What are the three subcategories of energy?
a. thermal energy: collective kinetic energy of the many particles in a substance (C, F or K)
b. gravitational potential energy: how gravity interacts with an object that has mass
- in space, an object has more gravitational energy when it is spread out than when it contracts
b. i. mass: a form of potential energy
- E=MC^2
- a small amount of mass can produce a large amount of energy
Describe the universal law of gravity?
Every mass attracts every other mass
- attraction is directly proportional to the product of their masses
- attraction is inversely proportional to the square of the distance between their centres
What can Newton’s third law help astronomers to do?
Estimate the mass of distant objects
What effects do gravity have on orbits?
- total orbital energy (gravitational and kinetic) remain constant if there is no external force
- orbits can gain or lose energy by having a gravitational encounter or by experiencing friction or atmospheric drag
What happens if an object gains enough orbital energy?
It can escape bound orbit to unbound orbit (escape velocity)
What is the escape velocity from earth?
11 km/s from sea level
How does the moon’s gravity affect earth?
- the shape of earth is bulged due to the moon’s gravitational pull
- it causes water to change tides
- the rotation of the earth is affected (it is slowed down due to the gravity of the moon pulling on earth)
What is the size of the tide affected by? Which phase is associated with which tide?
The size of the tides is affected by the phase of the moon (where the moon is in relation to the sun)
- a spring tide (highest tide) is associated with new and full moons
- a neap tide (lowest tide) is associated with the first and third quarter
What is tidal friction?
Friction with the rotating earth pulls the tidal bulges slightly ahead of the earth-moon line
What does tidal friction have an effect on?
The length of a day
- it increases by 1 second every 50,000 years
Is the rate of acceleration of an object dependent on its mass?
NO
