If the girl is also near the source of the sound, two alike sets of sounds will be heard.
Answer:

Explanation:
let the ladder is of mass "m" and standing at an angle with the ground
So here by horizontal force balance we will have

by vertical force balance we have

now by torque balance about contact point on ground we will have

so we will have

now from first equation we have


Answer:
the third law (for every action there is an equal and opposite reaction).
Explanation:
The skateboarder pushes backwards on the road (that is he applies a force on the road in a direction opposite the direction of intended motion). By Newton's third law, this action of the skateboarder causes an equal reaction of the road on the skateboarder in the opposite direction. Newton's third law states that action and reaction are equal but opposite in direction. So, the road in response to this backward force pushes the skateboarder in the forward direction causing the skateboarder and the skateboard to move in the forward direction.