Unit 1: Forces And motion- Kinematics Flashcards
What is Kinematics?
- The study of motion without regard for the cause
- Uses position, velocity, and acceleration to explain what is happening
What is dynamics?
- The study of the causes of motion.
- Considers initial conditions and laws of nature to explain why something is happening.
What is motion?
- Movement relative to a position or reference point.
What is a reference point (frame of reference)?
A random location from which the position of an object is being described.
What is uniform motion?
Movement in a straight line (same direction) at a constant speed.
What is non- uniform motion?
When direction and/or an object changes speed.
- called acceleration!
What is distance?
- The length of path travelled
- Scalar, summative
What is displacement?
- Change in position
- vector , direction aware
What is speed?
- distance travelled per time interval
- scalar
What is velocity?
- How fast an object changes its position
- Vector, direction aware
What is acceleration?
- The rate at which an object changes its velocity
- ex) Speeding up, slowing down, changing direction
What does the direction of an acceleration vector depend on?
- whether the object is speeding up or slowing down
- Whether the object is moving in the positive or negative direction
What is the general principle for determining acceleration?
If an object is slowing down, then its acceleration is in the opposite direction of its motion.
What do negative acceleration vectors refer to?
They do NOT refer to acceleration values that are less than zero. They are an acceleration in the opposite or negative direction.
Which of the following statements are true?
a) Distance is a vector quantity and displacement is a scalar quantity
b) A person makes a round-trip journey, finishing where she started. The displacement for the trip is 0 and the distance is some nonzero value.
c) A person starts at position A and finishes at position B. The distance for the trip is the length of the segment measured from A to B.
d) If a person walks in a straight line and never changes direction, then the distance and the displacement will have exactly the same magnitude.
e) The phrase “20 mi, Northwest” likely describes a distance for a motion.
f) The phrase “20 m, West” likely describes the displacement for a motion.
BDF
What is true about acceleration in the absence of air resistance?
All objects accelerate at the same rate. (-9.8m/s^2)
Assuming an object leaves and arrives at the same reference point:
- time up = time down
- vf = vi but magnitude only, one could be positive and one negative
Which of the following statements are true?
a) Velocity is a vector quantity and speed is a scalar quantity.
b) Both speed and velocity refer to how fast an object is moving.
c) Person X moves from location A to location B in 5 seconds. Person Y moves between the same two locations in 10 seconds. Person Y is moving with twice the speed as person X.
d) The velocity of an object refers to the rate at which an object’s position changes.
e) For any given motion, it is possible that an object could move very fast, yet have an abnormally small velocity.
f) The phrase, “30 mi/hr, West” likely refers to a scalar quantity
g) The average velocity of an object on a round-trip journey would be 0.
h) The direction of the velocity vector is dependent upon two factors: the direction the object is moving and whether the object is speeding up or slowing down.
ADEG
Which of the following statements are true?
a) The slope of a velocity-time graph is representative of the acceleration of the object
b) The area on a velocity-time graph is representative of the displacement
c) An accelerated object’s motion will be represented by a curved line on a velocity-time graph
d) Objects with positive acceleration will be represented by upwardly-curved lines on a velocity-time graph
e) A with zero slope on a velocity-time graph will be representative of an object which is at rest
AB
Which of the following statements about acceleration are true?
a) Acceleration, a vector quantity, is the rate at which the velocity changes.
b) Accelerating objects must be changing their speed
c) Accelerating objects must be changing their velocity
d) An object which is slowing down has acceleration
ACD
Which of the following statements are true?
a) A ball is thrown upwards, rises to its peak and eventually falls back to to the original height. As the ball rises, its acceleration is upwards, as it falls, its acceleration is downwards
b) A ball is thrown upwards, rises to its peak and eventually falls back to its original height. The speed which it is launched equals the speed at which it lands (assume negligible air resistance).
c) A very massive object will free fall at the same rate of acceleration as a less massive object.
d) The value of g on Earth is approximately 9.8 m/s^2.
BCD
