The total momentum is unchanged according to the law of conservation of momentum. When the gun is fired, the bullet gains a high velocity forward (positive velocity), and that velocity multiplied by its mass is the momentum the bullet gains. Therefore, the gun must gain a momentum backwards to cancel out that momentum forward, so the gun recoils back with a negative velocity.
Explanation:
It is given that,
Uncertainty in the speed of an electron, 
According to Heisenberg uncertainty principle,
is the uncertainty in the position of an electron
Since, 
So, the uncertainty in its position is 
. Hence, this is the required solution.
The statement about pointwise convergence follows because C is a complete metric space. If fn → f uniformly on S, then |fn(z) − fm(z)| ≤ |fn(z) − f(z)| + |f(z) − fm(z)|, hence {fn} is uniformly Cauchy. Conversely, if {fn} is uniformly Cauchy, it is pointwise Cauchy and therefore converges pointwise to a limit function f. If |fn(z)−fm(z)| ≤ ε for all n,m ≥ N and all z ∈ S, let m → ∞ to show that |fn(z)−f(z)|≤εforn≥N andallz∈S. Thusfn →f uniformlyonS.
2. This is immediate from (2.2.7).
3. We have f′(x) = (2/x3)e−1/x2 for x ̸= 0, and f′(0) = limh→0(1/h)e−1/h2 = 0. Since f(n)(x) is of the form pn(1/x)e−1/x2 for x ̸= 0, where pn is a polynomial, an induction argument shows that f(n)(0) = 0 for all n. If g is analytic on D(0,r) and g = f on (−r,r), then by (2.2.16), g(z) =
