Midterm Flashcards
Two skaters, an adult and a child, stand at rest on the ice, so their total momentum is zero. Then they push off each other. What happens s to their momentum so AFTER they push off of each other?
The total momentum of the two skaters is zero because the skaters have the same momentum, but in opposite directions
In a set, can a momentum be greater at the end of the experiment then it was at the beginning?
No. Throughout the experiment, the momentum stays the same as it was at the beginning. Only the velocity changes.
True or false: the total momentum BEFORE the collision is equal tho the momentum AFTER the collision.
True
How do you calculate the total momentum before the event?
M1(v1)+m2(v2)
So add the first mass times the first velocity to the second mass times the second velocity
How do you calculate the total momentum after the collision?
M1(v1)f+m2(v2)f=final momentum
Add the first mass x first velocity x force to the second mass x the second velocity x force
True or false
If you are changing the impulse of an object form 0 to a higher velocity, the longer you apply the force the greater the impulse, the amd the faster and object goes
True
What is conservation?
When the momentum before and after the collision is the same
What is explosion?
Objects start together but end apart
What are elastic collisions?
Objects start off apart, collide, and don’t stick
They start apart and end apart
What are non elastic collisions?
When objects start apart and end together
What is the “equation” of conservation of momentum?
P before collision = P after collision
What is centripetal force?
The force that keeps am object going in a circle
Define period
The time it takes to make an rotation
When a car is turning, what provides the centripetal force?
Friction
What provides the centripetal force when the earth is orbiting around the sun?
Gravity
Does a train going around in a circle at a constant speed have acceleration?
Yes; it is changing direction
Does a train going around in a circle at a constant speed change velocity?
Yes; it is changing direction
Which direction does the centripetal force always point?
To the middle
Which direction is the velocity pointing when an object is moving in a circle?
Perpendicular to the centripetal force
Which spool of thread is moving faster, the one on the outside of the record player or the inside?
The spool of thread on the outside; it has a greater distance to cover for the same amount if time.
Which spool of thread has a greater period, the one on the outside of the record player or the inside?
They have the same period
What factors affect the force of gravity between two objects?
Mass and distance
Does mass affect the force of gravity between two objects?
Yes
If you double the mass of one object, what happens to the force of gravity between the two objects?
It increases by a fourth
If you double the mass of both objects, what happens to the force of gravity between the two objects?
It doubles
If you double the distance between two objects what happens to the force of gravity between them?
It decreases by half
If you half the distance between two objects, what happens to the force of gravity between them?
It increases by a fourth
Why can’t you feel the force of gravitational pull between you and an apple?
The mass is too small
If you are in space, orbiting the earth, is there a force of gravity on you?
Yes.
If you are in space, orbiting the earth, why do you feel weightless
Because there is no Fn acting on you
What is Newton’s first law?
An object at rest stays at rest unless acted upon by an outside force, and an object in motion continues in a straight line at a constant velocity unless acted upon by outside forces.
Of you were in a spaceship, and fired a 15kg cannonball into frictionless space, after you fires the cannonball, how much force would you need to apply to keep it moving?
None, as there is no Ff to slow it down
What is the definition of inertia?
An object’s resistance to a change of motion
A car is moving at a constant velocity. What is the net force acting on it?
0
What is miu?
The coefficient of friction
What is miu affected by?
Surface texture and weight
Is miu affected by surface area?
No
What is air resistance?
Friction caused by air
What is air resistance NOT affected by?
Weight
What is air resistance affected by?
Surface area, aerodynamics, air density, and velocity
What is Newton’s second law?
Net force= mass x acceleration
Compare velocity and acceleration
Velocity is: how fast
Acceleration: how fast velocity CHANGES.
Two identical cars are traveling T 25mph. The first cars stops in 1s because it hits the wall. The second car stops in 5s because the driver hit the brakes. Which car has a greater change in momentum?
The change in momentum a are equal, because both start at 25mph, and end at 1.
Two identical cars are traveling T 25mph. The first cars stops in 1s because it hits the wall. The second car stops in 5s because the driver hit the brakes. What has a greater impulse, the brakes or the wall?
The impulses are the same
When doing problems on universal gravitation, and the question is talking about halving or multiplying the distance, what equation can you use?
(d1/d2) squared
