Chapter 2: Kinematics in 1D Flashcards
What is the equation to find displacement?
ΔX = X - Xo
What does ΔX mean?
Displacement
What does X mean regarding the displacement equation?
Final distance
What does Xo mean regarding the displacement equation?
Initial distance
What is the difference between distance and displacement?
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.
What is the equation for average velocity?
Vav = ΔX / Δt
What does Vav mean?
Average velocity
What does Δt mean?
Elapsed time
How do you find Δt?
Δt = t - to
What does t in the elapsed time equation represent?
Final time
What does to in the elapsed time equation represent?
Initial time
Velocity is a vector. How is it’s direction shown?
Through +/- signs
Usually, Vav has an arrow written above the V. Why is this not the case in 1 dimension?
The arrow shows the direction, but in 1 dimension the +/- sign shows direction
What is the average acceleration equation?
Aav = ΔV / Δt
What does Aav mean?
Average acceleration
What does ΔV mean?
Change in velocity
How do you find ΔV?
V - Vo
What does V mean in the changei n velocity equation?
Velocity
What does Vo mean in the change in velocity equation?
Initial velocity
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
A
A) Speeding up. If the signs match, you are speeding up. + or - do not show “speed” they show DIRECTION
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
B
B) Slowing down. The signs just show direction not speed.
What are the 5 variables of constant acceleration?
a = acceleration vector
ΔX = displacement vector
Vo = initial velocity vector
V = final velocity vector
t = time (not a vector)
How many of the 5 variables do you need to solve for constant acceleration?
3
What are the 4 equations for constant acceleration?
1) V = Vo + at
2) ΔX = 1/2 (Vo+V)t
3) V^2 = Vo^2 + 2aΔX
4) ΔX = Vot + 1/2at^2
What is the quadratic equation?
Ax^2 + Bx + C = 0
How can the quadratic equation be rearranged?
-B +/- √b2-4ac / 2a
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.
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
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?
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.
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
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
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
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
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?
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.
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
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
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
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
