B.
The explanation of the relationship between load and extension is not in Hooke's Law.
When you climb, earth exerts gravitational force on pack in downward direction(pointing towards the center of earth).
In order to climb, you need to work against work done by gravity on the pack.
Hence work done by you = work done by gravity on pack
= Force x displacement = 70 x 30 = 2100 J.
Answer:
The car slowing from 60 m/s to 0 m/s
Explanation:
The bird flying at 10m/s for 10 seconds will have the same speed for those 10 seconds. So we can say it doesn't have a varying speed (During those 10 seconds, we don't have any information about what happens later).
The fish moving at 2m/s for 5 minutes will have the same speed for those 5 minutes. So we can say it doesn't have a varying speed (During those 5 minutes, we don't have any information about what happens later).
The car traveling the speed limit, we know that his speed is the speed limit. It doesn't change.
The car slowing from 60 m/s to 0 m/s needs to change his speed in order to go from 60 m/s to 0 m/s. The speed will decrease progressively until the car completely stops.
Media 1 and 2 are air and liquid. By Snell's law;
n1/n2 = Sin ∅2/Sin ∅1
Then,
n2 = (n1* Sin Ф1)/Sin ∅2 = (1*Sin 31.7)/Sin 21.3 = 1.4466.
When the light travels in the opposite direction and at critical angle, media 1 and 2 are liquid and air respectively while ∅2 = 90°
Therefore,
n1/n2 = Sin 90 / Sin ∅c => ∅c = Sin ^-1[n2*Sin 90]/n1 = Sin ^-1[1*Sin 90]/1.4466 = 43.73°
The critical angle (∅c) is 43.73°.
Answer:
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