Answer:
a) W₁ = - 127 J
, b) W₂ = 148.18 J, c) = 3.43 m/s and d)
= 3.43 m / s
Explanation:
The work is given the equation
W = F. d
Where the bold indicates vectors, we can also write this expression take the module of each element and the angle between them
W = F d cos θ
They give us displacement, let's use Newton's second law to find strength, like the block has an equal acceleration (a = g / 7). We take a positive sign down as indicated
W-T = m a
T = W -m a
T = mg -mg/7
T = mg 6/7
T = 3.6 9.8 6/7
T = 30.24 N
Now we can apply the work equation to our problem
a) the force of the cord is directed upwards, the displacement is downwards, so there is a 180º angle between the two
W₁ = F d cos θ
W₁ = 30.24 4.2 cos 180
W₁ = - 127 J
b) the force of gravity is directed downwards and the displacement is directed downwards, the angle between the two is zero (T = 0º)
W₂ = (mg) d cos 0º
W₂ = 3.6 9.8 4.2
W₂ = 148.18 J
c) kinetic energy
K = ½ m v²
Let's calculate speed with kinematics
² = vo² + 2 a y
v₀ = 0
a = g / 7
² = 2g / 7 y
= √ (2 9.8 4.2 / 7)
= 3.43 m/s
We calculate
K = ½ 3.6 3.43²
K = 21.18 J
d) the speed of the block and we calculate it in the previous part
= 3.43 m / s
Answer:
370.6 nm
Explanation:
wavelength in vacuum = 494 nm
refractive index of water with respect to air = 1.333
Let the wavelength of light in water is λ.
The frequency of the light remains same but the speed and the wavelength is changed as the light passes from one medium to another.
By using the definition of refractive index
where, n be the refractive index of water with respect to air
By substituting the values, we get
λ = 370.6 nm
Thus, the wavelength of light in water is 370.6 nm.