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Level 55

Kinematics & Forces/Tension


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Explain the rules for vector addition
You can only directly add vectors if they are in the same direction.
True
t/f: science is collaborative
Is there acceleration for the horizontal component?
There is no acceleration in the horizontal component. The horizontal component of velocity is constant.
What is the time the projectile is in the air?
Ans: use the vertical component only- calculate the time it takes for the projectile to hit the ground.
How far did the projectile travel?
Ans: first get the time in the air by the vertical component. Then use the horizontal component's speed x time of flight. (Don't even think about over-analyzing and try to calculate the parabolic path).
magnetic field
a vector force field that surrounds any magnetic material
doing a weighted average for all the positions by their respective masses.
In a Cartesian coordinate, the center of mass is the point obtained by _______
Where is the center of mass going to be between the Earth and a chicken in space?
The center of mass of the Earth and a chicken in space is going to be almost at the center of the Earth, because the chicken is tiny, and its coordinate is weighted so.
What is the center of mass?
average position of all the particles of mass that make up the object
Where is the center of mass of a donut?
The center of mass of a donut is at the center of the donut (the hole).
Why do rockets work even in the vacuum of space.
For every action, there is an equal and opposite reaction
gravity
(physics) the force of attraction between all masses in the universe
circumference
2pi x r
What units are theta in, and what do they equal?
theta is always in radians. 2pi radians = 360 degrees.
no
Can you notice the force between two classmates?
What is the difference between frequency and period
frequency = how many times the object goes around the circle in one second.
False. mass is unrelated
T/F. The greater the mass, the greater the projectile height
t= square root of (2h/g)
Shortcut for solving for time of flight
False, it has a higher impact
T/F. Doubling velocity has the same impact on range as doubling g
This is due to _______.
Centripetal force is due to centripetal acceleration. Centripetal acceleration is due to changes in velocity when going around a circle. The change in velocity is due to a constant change in direction.
F=ma=mv^2/r
Centripetal force
Both toward the center of the circle
For centripetal motion, where is the direction of acceleration? Where is the direction of force?
Centripetal Force
A force directed towards the center of a circle that causes an object to follow a circular path
Why do you weigh more on an elevator that is accelerating up?
You weigh more on an elevator accelerating up because F=mg + ma, where a is the acceleration of the elevator.
Why do you weigh less on an elevator accelerating down?
You weigh less on an elevator accelerating down because F=mg - ma, where a is the acceleration of the elevator.
T/F. You are "weightless" when in space
False. you are not truly "weightless" when orbiting the Earth in space. You are simply falling toward the Earth at the same rate as your space craft.
What happens in regards to normal force and friction when something is laying on an inclined plane?
When something is laying still on an inclined plane, the normal force and friction force adds up in a vector fashion to equal the weight.
T/F. Kinetic friction is always larger than static friction.
False. Static friction is always larger than kinetic friction.
One component is normal (perpendicular) to the plane surface: FN = mg·cosθ
Gravity is divided into two components on an inclined plane. What are these two components
Describe what prevents an object from crashing through the surface of the inclined plane. Also, how does friction act?
To prevent the object from crashing through the surface of the inclined plane, the surface provides a normal force that is equal and opposite to the normal component of gravity.
In a non-moving object on an inclined plane...
In a non-moving object on an inclined plane: normal component of gravity = normal force; parallel component of gravity = static friction.
In an object going down the inclined plane at constant velocity......
In an object going down the inclined plane at constant velocity: parallel component of gravity = kinetic friction (yes, they're equal, don't make the mistake of thinking it's larger. Constant velocity = no acceleration = no net force).
In an object that begins to slip on the inclined plane.....
In an object that begins to slip on the inclined plane: parallel component of gravity > static friction.
In an object that accelerates down the inclined plane....
In an object that accelerates down the inclined plane: parallel component of gravity > kinetic friction.
When you push an object up an inclined plane, you need to overcome _______
When you push an object up an inclined plane, you need to overcome both the parallel component of gravity and friction.
components parallel to the plane
When you push or pull an object up an inclined plane the _______contributes to the motion
When there is no moving pully....
There are no moving pulleys here. If the weight of the box is 100 N, you have to pull with a force of 100 N. For every 1 meter you pull, the box goes up 1 meter.
When there is one moving pulley
the force needed to pull is halved because strings on both side of the pulley contribute equally. You supply 50 N (which is transmitted to the right-hand rope) while the left-hand rope contributes the o…
When there are two moving pulleys
Counting the ropes reveal that when we tug on one rope, it gets transmitted to a system where 4 ropes pull on the load. Thus, you can pull the 100 N box with onl…
Describe complex pulleys
Just like the simple pulleys, the ropes on both sides of the moving pulley contribute. Here, the left-most rope contributes also. This makes 3 contributing ropes, which makes the effort required to be reduce…
What are the 4 forces
The strong force: also called the nuclear force. It is the strongest of all four forces, but it only acts at subatomic distances. It binds nucleons together.
R=vo^2Sin2theta/g
Formula for range
0.5- 1.25m
Distance fallen after .5, 1, 2, 3, 4 ,5, and 8 seconds