The best way to think of 'per' is as the equivalent of 'for each'.
It hardens because you are pressing it against something.
Answer:

Explanation:
Given:
- Initial temperature of water,

- final temperature of water,

- energy spent in one hour of walk,

- volumetric capacity of stomach,

<em>Now, let </em><em>m </em><em>be the mass of water at zero degree Celsius to be drank to spend 450 kilo-calories of energy.</em>
We know:
.....................................(1)
where:
m = mass of water
Q = heat energy
temperature difference
= specific heat capacity of water
<u>Putting values in the eq. (1):</u>


Since water has a density of 1 kilogram per liter, therefore the volume of water will be:

Answer:
So where the red square is located it will be 90 °
And another will be 180-90-57= X
Answer:
R = (-2î − 6ĵ + 10k^)m
Explanation:
We are given;
D = (2î − 6ĵ)
Now, we want to find R such that,
D + R = −5Dĵ
Plugging in (2î − 6ĵ) for D in the R equation gives;
(2î − 6ĵ) + R = -5(2î − 6ĵ)j
(2î − 6ĵ) + R = -10k + 0
This is because in vector multiplication, i × j = k and j × j = 0
Thus;
(2î − 6ĵ) + R = -10k
Making R the subject gives;
R = -2î − 6ĵ + 10k^
Thus, the displacement vector R is;
R = (-2î − 6ĵ + 10k^)m