The potential energy of the block is A) 490 J
Explanation:
The potential energy of an object is the energy possessed by the object due to its position in the gravitational field.
It is calculated as follows:

where
m is the mass of the object
g is the acceleration due to gravity
h is the height of the object above the ground
For the block in this problem, we have:
m = 10 kg

h = 5 m
Therefore, its potential energy is:

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Volume = l*w*h = (18.1 cm)(19.2 cm)(20.3 cm) = 7,054 cm^3.
The horizontal velocity<span> of a projectile is </span>constant<span> (a never </span>changing<span> in value), There is a </span>vertical<span>acceleration caused by gravity; its value is 9.8 m/s/s, down, The </span>vertical velocity<span> of a projectile </span>changes<span> by 9.8 m/s each second, The </span>horizontal<span> motion of a projectile is independent of its </span>vertical<span> motion.</span>
Answer:

Explanation:
according to snell's law

refractive index of water n_w is 1.33
refractive index of glass n_g is 1.5


now applying snell's law between air and glass, so we have


![\beta = sin^{-1} [\frac{n_g}{n_a}*sin\alpha]](https://tex.z-dn.net/?f=%5Cbeta%20%3D%20sin%5E%7B-1%7D%20%5B%5Cfrac%7Bn_g%7D%7Bn_a%7D%2Asin%5Calpha%5D)
we know that 

THE MINI
Alec Issigonis, 1959
The Telephone
Alexander Graham Bell, 1876
http://www.radiotimes.com/news/2013-01-08/the-50-greatest-british-inventions