How do you represent the strength of a force in a free-body diagram?

Which one of the following research methods can show cause and effect

If frequency goes down, what happens to wavelength? does it get shorter or longer?

Check the following equation for dimensional homogeneity: ⅆ mv=∫t1t2(f⁢cosθ)ⅆt where m is mass, v is velocity, f is force, θ is an angle, and t is time. check that each term in the equation has the following dimensions: [malbec] where you are to choose the coefficients a, b, c.