the number of neutrons may b 21
1) First of all, let's find the resistance of the wire by using Ohm's law:

where V is the potential difference applied on the wire, I the current and R the resistance. For the resistor in the problem we have:

2) Now that we have the value of the resistance, we can find the resistivity of the wire

by using the following relationship:

Where A is the cross-sectional area of the wire and L its length.
We already have its length

, while we need to calculate the area A starting from the radius:

And now we can find the resistivity:
Explanation:
Given that,
Initial speed of the object, u = 1 m/s
Acceleration of the object, 
We need to find the time when the object comes at rest (v=0). Let it is given by :


t = 1 second
So, the object will comes to rest at 1 second. Hence, this is the required solution.
Answer:
Before: 0 m/s
After: -4 m/s
Explanation:
Before: Since you and your beau started at rest, your beau initial velocity is 0 m/s.
After: Since we have to conserve momentum,
momentum before push = momentum after push.
The momentum before push = 0 (since you and your beau are at rest)
momentum after push = m₁v₁ + m₂v₂ were m₁ = your mass = 60 kg, v₁ = your velocity after push = 3 m/s, m₂ = beau's mass = 45 kg and v₂ = beau's velocity.
So, m₁v₁ + m₂v₂ = 0
m₁v₁ = -m₂v₂
v₂ = -m₁v₁/m₂ = -60 kg × 3 m/s ÷ 45 kg = -4 m/s
So beau moves with a velocity of 4 m/s in the opposite direction