Ch. 4 Sec. 6&7 Flashcards
When an object is at rest what doesn’t it have?
- no acceleration
- no net force acting on it
What is an object at rest?
Sum of the forces on the object
When an object is moving at a constant speed what doesn’t it have?
No net force on it
What does the first law of motion not have?
No net force on it.
In the second law of motion what doesn’t it have?
No acceleration = no force
Are objects moving up or down at a constant speed the same or different?
Same
When roller coasters move up, what else moves up?
The acceleration moves up
What does Newton’s 2nd law show?
For acceleration going up the net force has to push up
What is air resistance?
The air applies a force to materials that oppose the force of gravity
What is apparent weight?
The net force acting on you by a surface in the direction toward earth.
If you accelerate upward what happens?
If you accelerate upward then your apparent weight is greater than your unaccelerated weight, because there is a greater force between you and the surface.
If you are traveling at a constant speed, what happens?
If you are traveling at a constant speed, your apparent weight is equal to your accelerated weight.
What is the equation for the centripetal force?
Fc=mv^2/r
What is the equation for centripetal acceleration?
ac=v^2/r
For an object traveling in a circular path at a constant speed what happens?
For an object traveling in a circular path at a constant speed, the centripetal acceleration and centripetal force are always perpendicular to the objects velocity.
What happens to roller coasters?
Roller coasters curve where the car tilts vertically and the wheels face outside of the circle the force is toward the center is normal force of the track on the wheels.
Are roller coasters parallel or perpendicular to the track?
Perpendicular
What is normal force?
Normal force is a constant force exerted on an object by the surface it is in contact with and it points perpendicular to the surface toward the object.
What is Fg at top do?
Acts down toward the center
What is Fz?
Weight-top and bottom are the same length since the car is the same weight
What is FN at the top?
It is smaller since the weight contributes = if speed is down the Fc is down
What is Fc?
Different lengths from top to bottom since there is larger speed at bottom of loop
What is the force on you in a car?
On a level track… The sum of forces is 0
What happens at the bottom of the loop?
The net force is toward center to keep moving in a circular motion
What happens at the top of the loop?
The net force is downward toward the center
What do astronauts do?
Astronauts test themselves to see how many g’s they can stand.
What does one g stand for?
9.8 m/s^2
What does roller coaster safety require?
Roller coaster safety requires 4g’s for entire ride
