Here you go it was too long to type
Answer:
If the combination of all the forces acting on an object sums upto be zero, then the net force is known as <u>balanced force.</u>
If the combination of all the forces acting on an object is non-zero, then the net force is said to be <u>unbalanced force. </u>The unbalanced force causes the object change the state of rest or motion.
No, he did not perform any work. Work is when you’re using energy which results in a force. Even though he was tired and sweaty, he did not move the boulder. So therefore he did not perform any work.
It takes twice the force to produce the same acceleration in the 2kg rock.
