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Two balls of mass 3kg and 7 kg respectively move towards one another with speeds 5ms^-1 and 2ms^-1 respectively on a smooth table. If they collide and join, what velocity do they move off with?

m = 3kg ; 7kg u = 5ms^-1 ; -2ms^-1 (Taking the direction to the right as positive). momentum before = m1u1 + m2u2 = (3x5) + (7x-2) = 1 momentum after = (m1+m2)v2 = (3+7)v = 10v By the principle of conserv...

Answered by Aimee G. • Physics tutor

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Find the angle at which total internal refraction takes place when light is going from glass to air.

The angle at which this takes place is called the critical angle.

We can apply Snell's law in this situation: n₁sin C1 = n₂sin (90deg)

sin C = n₂/ n

Answered by Catherine T. • Physics tutor

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Explain the photoelectric effect, when does it occur and what is its significance in understanding the nature of light ? (6)

metal (unlike insulators ) contains free electrons (1)

kinetic energy transferred from the light incident on the surface to the free electrons (1)

The maximum kinetic energy of the electrons...

Answered by Helena R. • Physics tutor

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The mercury atoms in a fluorescent tube are excited and then emit photons in the ultraviolet region of the elecrtomagnetic spectrum. Explain how the mercury atoms become excited.

The mercury atom is excited one of its electrons goes from an upper electron shell to a lower electron shell thanks to some energy that it recives from the outside. When an atom is excited it is instable ...

Answered by Marie B. • Physics tutor

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