the distance between a boy and a hill is 250 meters. if the boy shouts after how long will the echo be heard numerical problem​

1.5 s (approx.) and distance of echo traveled is 500m.

Explanation:

As you have not mentioned the speed of sound in the air, let's assume it to be 330 m/s.

Distance = velocity x time

Time = Distance / Velocity

= 250/330

 = 0.75 s (approx.)

This is the time for the sound from the boy to the hill.

An echo is formed from returning the sound from the hill back to the boy.

So, the time for the echo to be heard will be 2 times the time taken by sound from the boy to reach the hill.

So, echo time = 1.5 s

Distance traveled will be 250 + 250 = 500m. We are adding because it is returning back to the boy.

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.