# PHYSICS - Help needed, please and thank you! 1. Draw the FBDs for the following objects in italics. a) A tray of food is pushed horizontally east across a table. b) A child pulls on a string to...

PHYSICS - Help needed, please and thank you!

1. Draw the FBDs for the following objects in italics.

a) A tray of food is pushed horizontally east across a table.

b) A child pulls on a string to life a toy block.

gsenviro | Certified Educator

Dear deni89,

The free body diagrams of all the cases are attached in the image.

The normal force on the rock is the gravity or the rock's own weight. This force acts downwards. There is no other force in the normal direction.

The net horizontal force on the rock is the resultant of the force applied by the tractor on the rock and friction force. Since these two forces oppose each other, the net force is given by:

F net = F tractor - F friction = 1200-750 N = 450 N

Using the second law of motion, F = ma

thus, acceleration of the rock, a = F/m = 450/150 m/s^2 = 3 m/s^2

Hope this helps.

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deni89 | Student

2. A tractor pulls a 150kg rock to the right with a force of 1200 N againts a force of friction of 750 N [left].

a) Draw the FBD for the rock.

b) Find the normal force on the rock. Explain your reasoning.

c) Find the net force acting on the rock.

d) Find the acceleration of the rock.