Explanation:
Solution,
Volume (v)=287 cm^3
Mass(m)=816 g
Density(d)=m/v
=816/287
=2.84
So, the density of the block of marbles is 2.84 g/cm^3.
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Answer:
The air is contained at a high pressure in the tube. When it escapes from a small orifice, it suddenly expands. A large amount of its heat is absorbed in the process of expansion resulting in considerable fall in its temperature. This is why the escaping air feels cold.
Answer:

Explanation:
The frequency of a simple pendulum is given by:

where
g is the acceleration of gravity
L is the length of the pendulum
Calling
the length of the first pendulum and
the acceleration of gravity at the location of the first pendulum, the frequency of the first pendulum is

The length of the second pendulum is 0.4 times the length of the first pendulum, so

while the acceleration of gravity experienced by the second pendulum is 0.9 times the acceleration of gravity experienced by the first pendulum, so

So the frequency of the second pendulum is

Therefore the ratio between the two frequencies is

The answer is B tell me if I am wrong.
Answer:
Apparent depth (Da) = 60.15 cm (Approx)
Explanation:
Given:
Distance from fish (D) = 80 cm
Find:
Apparent depth (Da)
Computation:
We know that,
Refractive index of water (n2) = 1.33
So,
Apparent depth (Da) = D(n1/n2)
Apparent depth (Da) = 80 (1/1.33)
Apparent depth (Da) = 60.15 cm (Approx)