If the beam has a concentrated load acting on it in the center of the beam, then the deflection must satisfy the symbolic boundary value problem:
frac{d^4y}{dx^4} = -Fdelta(x-a),
where x = a is the point where the mass is applied. F is the force applied and the minus sign indicates that the force is downward. The end points of the beam satisfy the conditions
y(0) = 0, y''(0) = 0,
y(L) = 0, y''(L) = 0.
Problem 3. Suppose that the length of the beam is 4 m, and suppose that EI = 1. Further suppose that the force F = 2 is applied at x = 3. Then y(x) satisfies the boundary value problem
frac{d^4y}{dx^4} = -2delta(x-3),
with
y(0) = 0, y(4) = 0,
y''(0) = 0, y''(4) = 0.
Use the technique of the Laplace transform to determine the vertical deflection y(x). (Hint: Let y'(0) = A and y'''(0) = B. Use the formula L{y^{(n)}}(s) = s^nY(s) - s^{n-1}y(0) - s^{n-2}y'(0) - ... - y^{(n-1)}(0) for n = 4 to solve for the Laplace transform Y(s) of y(x) and then use the conditions y(4) = y''(4) = 0 to find A and B.)