How fast is a wave with a wavelength of 0.4 m and a frequency of 1000 hz travelling?
a. 0 m/s
b. 0.04 m/s
c. 400 m/s
d. 2500 m/s

Ineed the answer to question 1 , i’m desperate

What is the equation for electrical work?

Two steel balls, each of mass m, are welded to a light rod of length l and negligible mass and are initially at rest on a smooth horizontal surface. a horizontal force of magnitude f is suddenly applied to the rod as shown. determine (a) the instantaneous acceleration a of the mass center g and (b) the corresponding rate at which the angular velocity of the assembly about g is changing with time.