Unit 6 - Velocity and Momentum
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Describing Motion What is an objects change in position relative to a reference point?
motion when an object changes position with respect to a reference point, the object is said to be in motion.
Desribing Motion What is need to determine the position of an object?
a frame of reference
What is a coordinate system in which the position of the object is measured?
frame of reference in science, you can’t just say that something moved, you have to explain where it started and which way it went.
Distance vs Displacement What is the entire path traveled by an object?
distance
Distance vs Displacement What is the SI unit for distance
meters (m) since it is a scalar unit it doesn’t need a direction, opposed to displacement
Distance vs Displacement What is the distance and direction of the object’s change in position? the starting point to the ending point
displacement
Distance vs Displacement What is the SI unit for displacement?
meters (m) and direction since displacement is a vector quantity it needs a direction, opposed to distance.
Distance vs Displacement Solve: Sally runs 50m East and then turns around and runs 30m West. What is Sally’s displacement? this is looking for displacement, not distance
20 meters East • includes a direction • if they are opposing directions, subtract and take the left over amount
Distance vs Displacement Solve: Sally runs 50m East and then turns around and runs 30m West. What is Sally’s distance? looking for distance, not displacement
80 meters add all distances together
Speed and Velocity What is the formula for velocity and speed?
s = d/t or v = d/t their formulas are the same, but the answer for velocity has a direction
Speed and Velocity What is the SI unit for speed?
meters per second (m/s) this is a scalar quanity, it doesn’t need direction
Speed and Velocity What is the SI unit for Velocity?
meters per second (m/s) and a direction this is a vector unit and needs direction
Speed and Velocity What is the speed of an object when it covers equal distances in equal amounts of time?
constant speed constant = unchanging, so the speed is not is not changing example: sally is going a constant speed of 10 m/s. if this was constant acceleration, it would be constantly accelerating equal amounts. example: Sally’s is in constant acceleration and is accelerating a constant speed of 10 m/s. every second she is going 10 m/s faster.
Speed and Velocity What is the TOTAL distance of the object’s travel divided by the object’s TOTAL time of travel?
average speed this means the formula is average speed = total distance/total time ex: the whole trip i averaged 10 m/s
Speed and Velocity What is the speed measured in a small time interval? hint: a car’s spedometer measure it
instantaneous speed the smaller the time interval, the more accurate the speed will be Describes what you are doing right now example: right now im going 10 m/s
Speed and Velocity Is speed a scalar or vector quantity?
scalar, it doesnt need a direction
Speed and Velocity Is velocity a scalar or vector quantity?
vector, it needs a direction “im vector, fighting crime with both direction and magnitude (m/s), OH YEAAH”
Speed and Velocity Is it possible for two cars to have the same speed, but different velocity? yes or no
Yes, if the car turns, the car’s velocity changes because the direction has changed.
Relative and Resultant Motion What is the sum of all the velocities of an object relative to a particular reference point?
resultant velocity you find this by using vector addition. Since velocity has both speed and direction, you can’t just add the numbers; you have to account for which way they are pointing:
Distance and Displacement Is distance a scalar or vector quantity?
scalar, it doesnt need a direction, only magnitude (m)
Distance and Displacement Is displacement a scalar or vector quantity?
vector, it needs a direction “I’m vector, fighting crime with BOTH direction and magnitude (m) oH EYEAH”
Relative and Resultant Motion Is Relative and Resultant Motion scalar or vector?
They are BOTH vectors Why they are both vectors: Resultant Velocity: It tells you the final speed and the final direction an object is moving (e.g., 53 mph North). Relative Velocity: It tells you how fast an object looks from your perspective and which way it appears to be going (e.g., a car appearing to move backward at 10 mph South because you are passing it).
Resultant and Relative Motion What is the difference between relative and resultant motion?
Resultant Motion: The total movement. You add all the forces together to see where the object actually ends up Relative Motion: The point of view. It’s how fast something looks to you based on the reference point’s point of view Example of Resultant: You walk forward on a moving bus. Your speed + the bus’s speed = Resultant. Example of Relative: You pass a car on the highway. It looks like it’s moving slowly to you, even though you’re both going fast = Relative.
Relative and Resultant Motion IMPORTANT FOR UNDERSTANDING: Explain what relative and resultant motion will look like in a problem
When a problem is about a outside still object, viewing a moving object; it is asking about relative motion When a problem is talking about a object within another object (like a bus) it is asking about resultant motion