How does a vacuum flask keep drinks hot? Explain in terms of conduction, convection and radiation.
1 answer:
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Answer:
1. Running velocity (5 m/s)
2. Resting velocity (0 m/s)
3. Walking velocity (-1 m/s)
1. Running speed (5 m/s)
2. Walking speed (1 m/s)
3. Resting speed (0 m/s)
Explanation:
Attached you will find the plot of position vs time of Ellie´s movement.
The velocity is the displacement of the object over time relative to the system of reference. The speed, in change, is the traveled distance over time in disregard of the system of reference.
So, the velocity is calculated as follows:
v = Δx / Δt
where
Δx = final position - initial position
Δt = elapsed time
1) The average velocity of Ellie while running is:
v = 1000 m - 0 m / 200 s = 5 m/s
While resting:
v = 0 m - 0 m / 100 s = 0 m/s
And while walking back:
v = 0 m - 1000 m / 1000 s = - 1 m/s
Note that in this last case, the initial position is 1000 m because Ellie is 1000 m from the origin of the system of reference when she walks back. The final position will be the origin of the system of reference, 0 m.
Comparing with the graphic, the velocity is the slope of the function position(t).
Then:
1. Running velocity (5 m/s)
2. Resting velocity (0 m/s)
3. Walking velocity (-1 m/s)
2) The speed is the distance traveled over time:
Running speed = 1000 m / 200 s = 5m /s
Resting speed = 0 m / 100 s = 0 m/s
Walking speed = 1000 m/ 1000 s = 1 m/s
Then:
1. Running speed (5 m/s)
2. Walking speed (1 m/s)
3. Resting speed (0 m/s)
