Answer:

Explanation:
The velocity v₁ can be calculated with the kinematic formula:

Since the object is initially at rest, v₁ becomes:

Where g is the acceleration due to gravity. Now, the velocity v₂ can be calculated with the same formula, but now the initial velocity is v₁:

Substituting v₁ in this expression and solving for v₂, we get:

Now, dividing v₂ over v₁, we get the expression:

It means that v₂ is √2 times v₁.
A, convection, is your answer
Answer:
A = 1.54 x 10⁻⁵ m² = 15.4 mm²
Explanation:
The resistance of a wire can be given by the following formula:

where,
A = smallest cross-sectional area = ?
ρ = resistivity of copper = 1.54 x 10⁻⁸ Ωm
= resistance per unit length of wire = 0.001 Ω/m
Therefore,

<u>A = 1.54 x 10⁻⁵ m² = 15.4 mm²</u>
To solve this exercise we need the concept of Kinetic Energy and its respective change: Initial and final kinetic energy.
Let's start considering that the angular velocity is given by,

Where,
V = linear speed
R = the radius
In the case of the initial kinetic energy:

Where I is the moment of inertia previously defined.

In the case of the final kinetic energy, we have to,


For conservation of Energy we have, that
, then (canceling the mass and the radius)




