Question

1. Calculate the kinetic energy of a body of mass 0.1 kg and momentum 80 kg ms-¹.

2. The wavelength of redlight is 800 nm. Find its frequency. 
Speed of light = 3×10⁸ ms-¹.

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Answer 1

Answer:

1) K.E =P Square/2m

=20×20/(2×0.1)

=2000Joule.

2)speed of light =3×10 to the power of 8m per s

Wavelength of red light is 800nm.

Frequency =speed/ wavelength

Frequency =3×10 to the power of 8/ 800

Frequency =3×10 to tge power of 15/8s

Frequency =0.375 ×10 to the power of 15 Hz.

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Answer 2

Answer:

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1. K.E. = 1/2mv2 and momentum P = mv

Eliminating v, K.E. = 1/2m x (P/m) = P2/2m

Given: P = 40 kg m/s, m = 0.1 kg.

K.E. = (40)2/2 x 0.1 = 8000 J = 8 x 103 J.

2. Velocity of wave is given as

• v = fλ

• where f = frequency

• and λ = wavelength

Case (1)

$v \: = \: 3 \times {10}^{8} {ms}^{ - 1}$

$λ=4000 \: 400 \times {10}^{ - 9m}$

As we know, fλ = v

$∴ \: f= \: \frac{v}{λ}$

$= \frac{3 \times {10}^{8} }{400 \times {10}^{9} }$

$= .75 \times {10}^{13} hz$

$f = 7.5 \times {10}^{14} hz$

$= 7.5 \times {10}^{14} . \: 3.75 \times {10}^{14}$

Required Answer ☝️