Chapter 2: Kinematics in 1D

Question 1

What is the equation to find displacement?

Answer 1

ΔX = X - Xo

Question 2

What does ΔX mean?

Answer 2

Displacement

Question 3

What does X mean regarding the displacement equation?

Answer 3

Final distance

Question 4

What does Xo mean regarding the displacement equation?

Answer 4

Initial distance

Question 5

What is the difference between distance and displacement?

Answer 5

Distance is the overall amount traveled, while displacement is the amount between the starting and finishing point.

For example, a swimmer does 6 laps in a 50m pool. Their DISTANCE is 300m but their DISPLACEMENT is 0m.

Question 6

What is the equation for average velocity?

Answer 6

Vav = ΔX / Δt

Question 7

What does Vav mean?

Answer 7

Average velocity

Question 8

What does Δt mean?

Answer 8

Elapsed time

Question 9

How do you find Δt?

Answer 9

Δt = t - to

Question 10

What does t in the elapsed time equation represent?

Answer 10

Final time

Question 11

What does to in the elapsed time equation represent?

Answer 11

Initial time

Question 12

Velocity is a vector. How is it’s direction shown?

Answer 12

Through +/- signs

Question 13

Usually, Vav has an arrow written above the V. Why is this not the case in 1 dimension?

Answer 13

The arrow shows the direction, but in 1 dimension the +/- sign shows direction

Question 14

What is the average acceleration equation?

Answer 14

Aav = ΔV / Δt

Question 15

What does Aav mean?

Answer 15

Average acceleration

Question 16

What does ΔV mean?

Answer 16

Change in velocity

Question 17

How do you find ΔV?

Answer 17

V - Vo

Question 18

What does V mean in the changei n velocity equation?

Answer 18

Velocity

Question 19

What does Vo mean in the change in velocity equation?

Answer 19

Initial velocity

Question 20

If you have an object and the velocity and acceleration are the same sign (++ / –) are you speeding up or slowing down?

A) Speeding up
B) Slowly down
C) Depends on the sign

Answer 20

A

A) Speeding up. If the signs match, you are speeding up. + or - do not show “speed” they show DIRECTION

Question 21

If you have an object where the acceleration and velocity are opposite signs (+- / -+) are you speeding up or slowing down?

A) Speeding up
B) Slowing down
C) They cancel each other out

Answer 21

B

B) Slowing down. The signs just show direction not speed.

Question 22

What are the 5 variables of constant acceleration?

Answer 22

a = acceleration vector
ΔX = displacement vector
Vo = initial velocity vector
V = final velocity vector
t = time (not a vector)

Question 23

How many of the 5 variables do you need to solve for constant acceleration?

Answer 23

3

Question 24

What are the 4 equations for constant acceleration?

Answer 24

1) V = Vo + at
2) ΔX = 1/2 (Vo+V)t
3) V^2 = Vo^2 + 2aΔX
4) ΔX = Vot + 1/2at^2

Question 25

What is the quadratic equation?

Answer 25

Ax^2 + Bx + C = 0

Question 26

How can the quadratic equation be rearranged?

Answer 26

-B +/- √b2-4ac / 2a

Question 27

The x-components has a value of -9.60 and the Y-component has a value of 7.05. If a magnitude, A, has these two components, what is the magnitude of A’s vector?

Draw it out.

Answer 27

A = 11.9

Explanation:
C^2 = A^2 + B^2
A^2 = X^2 + Y^2
A^2 = -9.6^2 + 7.05^2
A = square root of -9.6^2 + 7.05^2
A = 11.9

Question 28

If Vector A has a magnitude of 13.9 and its direction is 320 degrees counter-clockwise from the +x axis. What are the x and y components?

Answer 28

Ax = 10.6
Ay = -8.93

Explanation:
Ax = Acos(θ)
Ay = Asin(θ)

Ax = 13.9 * cos(320)
Ax = 10.6

Ay = 13.9 * sin(320)
Ay = -8.93

-8.

Question 29

A squirrel runs along an overhead telephone wire that stretches from the top of one pole to the next. It is initially at position xi=2.37m, as measured from the center of the wire segment. It then undergoes a displacement of Δx=-5.25m. What is the squirrel’s final position?

Xf = ? meters

Answer 29

Xf = -2.88 meters

Explanation:
1. Get needed equation: ΔX = ΔXf - ΔXi
2. Rearrange: xf = xi + Δx
3. Plug in known numbers: xf = 2.37m - 5.25m
4. Solve: xf = -2.88m

Question 30

Regarding a graph of position over time, what determines the “fastest” point of the object’s movement

A.) No slope
B) Highest point in the chart
C) Gradually slope
D) Steepest slope

Answer 30

D) Steepest slope

Explanation: A steeper slope on a position vs. time graph indicates the most movement in the shortest amount of time.

See question #2 in 1D Kinematics Achieve Homework for image

Question 31

On a position vs time graph with no straight lines (no easily visible slopes) how do you determine when the object was at it’s slowest?

Answer 31

If the object is not changing position, it is not moving. Meaning the closet spot to a horizontal line is where the speed is the slowest.

See question #3 in 1D kinematics achieve homework for image.

Question 32

A gnat takes off from one end of a pencil and flies around erratically for 32.6 seconds before landing on the other end of the same pencil. If the gnat flew a total distance of 7.65 meters, and the pencil is 0.0413 meters long, find the gnat’s average speed and the magnitude of the gnat’s average velocity.

Average speed: _____ m/s
|Average velocity|: _____ m/s

Answer 32

Average speed: 0.235 m/s
Average velocity: 1.27x10^-3

Explanation for average speed:
1. Find equation: average speed = distance / time
2. Plug in known numbers: Average speed = 7.65m / 32.6 s
3. Solve: average speed = 0.235 m/s

Explanation for average velocity:
1. v = d/t (d = displacement)
2. v = 0.0413m / 32.6 s
3. v = 0.00127 m/s or 1.27 x 10^-3

Question 33

The speed of propagation of the action potential (an electrical signal) in a nerve cell depends (inversely) on the diameter of the axon (nerve fiber). If the nerve cell connecting the spinal cord to your feet is 1.0m long and the nerve impulse speed is 19 m/s, how long does it take for the nerve signal to travel the distance?

time: _____ seconds

Answer 33

Time: 5.3x10^-2 seconds

Explanation:
1. Find equation: speed = distance / time
2. Rearrange: time = distance / speed
3. Plug in known numbers: time = 1.0m / 19m/s
4. Solve: time = 0.053 seconds or 5.3 x10^-2 seconds