One-Dimensional Kinematics (Ch. 2.1 - 2.7)

Question 1

mechanics

Answer 1

• the study of objects in motion
• includes kinematics and kinetics

Question 2

kinematics

Answer 2

• describes how objects move and predicts the objects’ motion
• approaches problems with the kinematic equations

Question 3

kinematic variables

Answer 3

• distance (d)
• displacement (x)
• speed (s)
• velocity (v)
• acceleration (a)
• time (T)

Question 4

scalar quantity

Answer 4

• magnitude only

Question 5

vector quantity

Answer 5

• magnitude AND direction

Question 6

distance (d)

Answer 6

• the total length of travel
• always positive
• scalar quantity
• SI units: meter (m)

Question 7

displacement (x)

Answer 7

• the net change in position
• positive, negative, or zero
• vector quantity
• SI units: meter (m)

ΔX = X_f - X_i

Question 8

distance vs. displacement

Answer 8

• d is scalar and x is vector
• different magnitude if there is a change in direction
• x can be zero while d has magnitude if start and stop at the same point

Question 9

speed (s)

Answer 9

• the rate of change of the distance
• always positive
• scalar
• SI units: m/s

s = d/Δt

Question 10

velocity (v)

Answer 10

• the rate of displacement
• positive or negative
• vector quantity
• SI units: m/s

V_av = Δx/ Δt

Question 11

speed vs. velocity

Answer 11

• the magnitude of both will only be different if the distance and displacement are different
• if the object changes direction, the magnitude of the speed and velocity will be different

Question 12

average velocity vs instantaneous velocity

Answer 12

• average velocity: the rate of change of the displacement over a period of time
• instantaneous velocity: the change in the position at an instant of time
• the average v = the instantaneous v if the velocity is constant

Question 13

acceleration (a)

Answer 13

• the rate of change of velocity
• positive or negative (indicates the direction of a)
• vector
• SI units: m/s²

V_av = Δx/ Δt

Question 14

average acceleration vs instantaneous velocity

Answer 14

• if the acceleration is constant, the average acceleration is equal to the instantaneous acceleration

Question 15

the sign of acceleration

Answer 15

• indicates direction of acceleration
  
  • ​the direction of acceleration is determined by the sign from the change in velocity, not by the direction an object is moving in
• acceleration does not have to point in the same direction as the velocity
• a negative acceleration does not necessarily mean the object is slowing down; it just means the acceleration is pointing in the negative direction

Question 16

velocity vs. acceleration

Answer 16

• when the velocity and acceleration of an object have the same sign (point in the same direction), the speed of the object increases.
• when the velocity and acceleration of an object have opposite signs (point in opposite directions), the speed of the object decreases

Question 17

the relationship of speed to velocity and acceleration

Answer 17

• increases when velocity and acceleration have the same sign (direction)
• decrease when velocity and acceleration have the opposite sign (direction)

Question 18

graphing relationships of velocity

Answer 18

• the slope of a position vs time graph = velocity

m = Δx / Δt = V

Question 19

graphing relationships of acceleration

Answer 19

• the slope of the velocity vs. time graph = acceleration

m = Δv / Δt = a

Question 20

graphs of constant position

Answer 20

• the slope of a position vs time graph is 0, as it is constant
• therefore, v = 0 and a = 0

Question 21

graphs of constant velocity

Answer 21

• the position vs time graph displays a slope, indicating a change in position
• the slope of the velocity vs time graph is zero, indicating a constant velocity
• therefore, a = 0

Question 22

graphs of constant acceleration

Answer 22

• both the position vs time graph and the velocity vs time graph indicate changes in position and velocity
• therefore the slope of a is zero, and it has a constant acceleration

Question 23

position vs time graph

Answer 23

• a graphical representation of velocity
• the average velocity is the slope of the straight line connecting two points corresponding to a given time interval
• the instantaneous velocity is the slope of the tangent line (the straight line that just touches the curve) at a given instant of time
• with constant velocity, the average velocity over any time interval is equal to the instantaneous velocity at any time

Question 24

velocity vs. time graph

Answer 24

• a graphical representation of acceleration
• the average acceleration is the slope of the straight line connecting two points corresponding to a given time interval
• the instantaneous velocity is the slope of the tangent line (the straight line that just touches the curve) at a given instant of time
• with constant acceleration, the average velocity over any time interval is equal to the instantaneous velocity at any time

Question 25

Kinematic equations

Answer 25

Question 26

free fall

Answer 26

* an object only under the influence of gravity (air resistance is negligible)

Question 27

acceleration in free fall

Answer 27

* ALL objects experience a *downwards* acceleration of 9.8 m/s² regardless of mass * At EVERY point of the object's travel, the acceleration is 9.8 m/s² downwards * "at every second, add 9.8 m/s velocity in the negative direction"

Question 28

velocity and acceleration at the top of an object's free fall

Answer 28

* the velocity = 0 * the acceleration = 9.8 m/s² downwards

Question 29

the velocity of the object as it travels up the velocity of the object as it travels down

Answer 29

* the object slows down as it moves up, as a and v are in opposite directions * the object speeds up as it moves down, as a and v are in the same direction

Question 30

the magnitude of velocity at the same heights

Answer 30

* at the same height, the velocity up and the velocity down have the same magnitude but opposite directions