ANSWER
625 m/s
EXPLANATION
Given:
• The frequency of the sound wave, f = 250 Hz
,
• The wavelength, λ = 2.5 m
Find:
• The speed of the wave, v
The speed of a wave of wavelength λ and frequency f is given by,

Substitute the known values and solve,

Hence, the speed of the wave is 625 m/s.
Rigidbodies are components that allow a GameObject<u> to react to real-time physics. </u>
Explanation:
- Rigidbodies are components that allow a GameObject to react to real-time physics. This includes reactions to forces and gravity, mass, drag and momentum. You can attach a Rigidbody to your GameObject by simply clicking on Add Component and typing in Rigidbody2D in the search field.
- A rigidbody is a property, which, when added to any object, allows it to interact with a lot of fundamental physics behaviour, like forces and acceleration. You use rigidbodies on anything that you want to have mass in your game.
- You can indeed have a collider with no rigidbody. If there's no rigidbody then Unity assumes the object is static, non-moving.
- If you had a game with only two objects in it, and both move kinematically, in theory you would only need a rigidbody on one of them, even though they both move.