If the speed of sound in air is 340 m/s which strike with an obstacle at distance of 30 m. Find the time to heard an echo?

Please answer fast

In which of the following cases is work being done on an object? question 2 options: pulling a trailer up a hill carrying a box down a corridor suspending a heavy weight with a strong chain pushing against a locked door

Kate is working on a project in her tech education class. she plans to assemble a fan motor. which form of energy does the motor convert most of its electric energy into? a. light energy b. motion energy c. sound energy d. thermal energy

Lin yao looks at the back of a spoon. how should she describe her reflection? upside down and smaller upside down and larger right-side up and smaller right-side up and larger