Oct 7/9th - Newton's laws and orbits Flashcards
Speed
how far something will go in a certain amount of time.
Velocity
tells us both its speed and its direction.
Acceleration
velocity is changing in any way, whether in speed or direction or both.
Note that while we normally think of acceleration as an increase in speed, in science we also say that you are accelerating when you slow down or turn
Slowing represents a negative acceleration, causing your velocity to decrease. Turning means a change in direction—which therefore means a change in velocity—so turning is a form of acceleration even if your speed remains constant.
Acceleration of Gravity
Acceleration of a falling object
9.8 meters/sec, or about 10 m/s SQUARED
Gravity accelerates all objects by the same amount, regardless of their mass
How does air resistance affect gravity?
can cause differences in acceleration: If you dropped a feather and a rock on the Moon, where there is no air, both would fall at exactly the same rate
Momentum
the product of its mass and velocity; that is, momentum = mass × velocity.
How can we change an object’s momentum?
The only way to change an object’s momentum is to apply a force to it.
EX: in a collision, an object transfers some momentum to your car and furthermore exerts force
Changing an object’s momentum means changing its velocity, as long as its mass remains constant.
Net Force
represents the combined effect of all the individual forces put together
A change in momentum occurs only when the net force is not zero
Angular momentum
which you can also think of as “circling momentum” or “turning momentum.”
Any object that is either spinning or moving along a curved path has angular momentum
Earth has angular momentum due to its rotation (rotational angular momentum) and to its orbit around the Sun (orbital angular momentum)
How can angular momentum be changed (what special force is needed?)
The type of force that can change an object’s angular momentum is called a torque, which you can think of as a “twisting force.”
How is mass different than weight?
Your mass is the amount of matter in your body.
Your weight (or apparent weight*) is the force that a scale measures when you stand on it; that is, weight depends both on your mass and on the forces (including gravity) acting on your mass.
Free-Fall
falling without any resistance to slow you down.
The floor drops away at the same rate that you fall, allowing you to “float” freely above it, and the scale reads zero because you are no longer held to it. In other words, your free-fall has made you weightless.
Weightlessness in space:
Many people guess that there’s no gravity in space, but that’s not true. After all, it is gravity that makes the Space Station orbit Earth.
Astronauts are weightless for the same reason that you are weightless when you jump off a chair: They are in a constant state of free-fall.
With enough speed, you can continuously “fall” around earth; you’d be in orbit
The Space Station and all other orbiting objects stay in orbit because they are constantly “falling around” Earth
Newton’s Laws of Motion
1: Newton’s first law: An object moves at constant velocity if there is no net force acting upon it
2: Newton’s second law of motion tells us what happens to an object when a net force is present
3: Newton’s third law: For any force, there is always an equal and opposite reaction force.
Newton’s first law: An object moves at constant velocity if there is no net force acting upon it
In other words, objects at rest (velocity=0) tend to remain at rest, and objects in motion tend to remain in motion with no change in either their speed or their direction.
also explains why you don’t feel any sensation of motion when you’re traveling in an airplane on a smooth flight. As long as the plane is traveling at constant velocity, no net force is acting on it or on you.
