I\'m having a hard time understanding the concepts please, explain this in detai

Question

I'm having a hard time understanding the concepts please, explain this in detail, as if this person didn't know much about physics. Thanks!!

Question 2 (20 points) A boy pushes on a door: PULL MIDVALE SCHOOL FOR THE GIFTED (a) The 45.0 kg boy pushes the 10.0 kg door with a force of 301 N. What is the magnitude and direction of the force of the door on the boy? [5] Briefly explain your answer [5 b) Suppose a man pushes the door from the inside. How does the force exerted by the door on the boy compare to the force exerted by the boy on the door? 15 (c) The boy gets tired of pushing against the door and walks around the building looking for another way in. Unable to find a different entrance, he returns to the same spot having traveled a total distance of 20.0 meters. Is there enough information to tell his average velocity for the entire journey? Explain briefly. [5

Explanation / Answer

a) The door exerts and equal force on the boy but in the opposite direction. That is when the boy exerts a force of 301 Newtons, the door exerts the same amount of force on the boy. This is due to newton's third law of motion, every action has an equal and opposite reaction. Now why does the door open? that is due to the turning effect caused by the force applied by the boy. Such a turning effect is called torque. You always apply the force on the edge of the door and not on the middle, because further the distance from the turning point the greater is the turning effect/torque. Torque is given by r x F, where r is the distance between point of turning and the point of application of force F

b) When a man is pushing the door from the inside, the reaction force due to the door and the force due to the man both act on the boy, therefore, it will be more difficult for the boy to open the door. Because extra force has to be applied by the boy to counter the man's force to turn the door.

c) average velocity is total displacement/total time
displacement is the shortest distance between starting point and end point, here both the starting and the end points are the same as the boy returns to where he started hence the average velocity is 0 m/s

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