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Answer : 6.022• 10^23 atoms of potassium
Answer:
220 A
Explanation:
The magnetic force on the floating rod due to the rod held close to the ground is F = BI₁L where B = magnetic field due to rod held close the ground = μ₀I₂/2πd where μ₀ = permeability of free space = 4π × 10⁻⁷ H/m, I₂ = current in rod close to ground and d = distance between both rods = 11 mm = 0.011 m. Also, I₁ = current in floating rod and L = length of rod = 1.1 m.
So, F = BI₁L
F = (μ₀I₂/2πd)I₁L
F = μ₀I₁I₂L/2πd
Given that the current in the rods are the same, I₁ = I₂ = I
So,
F = μ₀I²L/2πd
Now, the magnetic force on the floating rod equals its weight , W = mg where m = mass of rod = 0.10kg and g = acceleration due to gravity = 9.8 m/s²
So, F = W
μ₀I²L/2πd = mg
making I subject of the formula, we have
I² = 2πdmg/μ₀L
I = √(2πdmg/μ₀L)
substituting the values of the variables into the equation, we have
I = √(2π × 0.011 m × 0.1 kg × 9.8 m/s²/[4π × 10⁻⁷ H/m × 1.1 m])
I = √(0.01078 kgm²/s²/[2 × 10⁻⁷ H/m × 1.1 m])
I = √(0.01078 kgm²/s²/[2.2 × 10⁻⁷ H])
I = √(0.0049 × 10⁷kgm²/s²H)
I = √(0.049 × 10⁶kgm²/s²H)
I = 0.22 × 10³ A
I = 220 A
Answer:
The speed should be reduced by 1/√2 or 0.707 times
Explanation:
The relationship between the kinetic energy, mass and velocity can be represented by the following equation:
K.E = ½m.v²
In this equation, the mass is inversely proportional to the square of the velocity or speed. This means that as the mass increases, the speed reduces by × 2.
Let; initial mass = m1
Final mass = m2
Initial velocity = v1
Final velocity = v2
According to the question, if the mass of the body is doubled i.e. m2 = 2m
½m1v1² = ½m2v2²
½ × m × v1² = ½ × 2m × v2²
Multiply both sides by 2
(½ × m × v1²)2 = (½ × 2m × v2²)2
m × v1² = 2m × v2²
Divide both sides by m
v1² = 2v2²
Divide both sides by 2
v1²/2= v2²
Square root both sides
√v1²/2= √v2²
v1/√2 = v2
v2 = 1/√2 v1
This shows that to maintain the same kinetic energy if the mass is doubled, the speed should be reduced by 1/√2 or 0.707 times.
