Answer:
they cant travel through a vacuum
Answer: 0.85 meters (with and without sigfigs)
Explanation: To find the wavelength, you just have to switch around the equation for wave speed: v (wave speed) = λ (wavelength)*f (frequency) so λ (wavelength) = v (wave speed)/f (frequency). You don't have the wave speed but you can calculate it. Since wave speed is measured in meters/second or m/s, you just have to divide the amount of meters you were given by the amount of seconds. You will get 340 m/s. Next, you have to plug the values into the equation: λ (wavelength) = 340 m/s (wave speed)/400 Hz (frequency). The answer is 0.85 meters (seconds cancel) and has the correct number of significant figures.
Inertia is the name. Inertia is when a moving object stays in motion unless stopped by an outside force. This is Newton’s first law of motion
They are both Simple mechanics