8. Two students are having the following conversation about a 3rd student who
is sitting at rest in their chair
Student1: There are only 2 forces acting on student 3, the normal
force and the weight force. That means that these two forces are
Newton's 3rd law pairs (equal in magnitude and opposite direction)
Student 2: I think the forces are equal and opposite directions but I
don't think they are examples of Newton's third law pair of forces. I
think they are equal and opposite by Newton's second law not
Newton's 3rd law.
Which student do you agree with and why?

9. You push on a block with a force of 10 N. You make an observation that the
block as an acceleration of 3.6 m/sec2. Calculate the mass of the block.

10. Two train cars are connected by a rope. If each train car has a mass of 3,000
kg, and the system is observed to accelerate at a rate of 100 m/sec, calculate
the force needed to make this system move.

8) I agree with student 1 who says that there only two forces acting on student 3, the normal force and weight force. That means these two forces are Newton's third law pairs(equal in magnitude and opposite in direction).

9) Mass of the block is 2.77 kg

10) The force needed to make this system move is 600,000 N

Explanation:

8. The weight of the book acts as a downward force and the table on which the book is lying exerts a normal force in the upward direction on the book. The weight W and normal force N are equal in magnitude and opposite in direction. Hence I agree with Student 1.

9)Given:

Force=10 N

Acceleration (a)=3.6 m/sec2

Solution:

Thus the Mass of the block is calculated to be 2.77 kg.

10)Given:

Mass of the train1=3000 kg.

Mass of train 2=3000 kg.

Solution:

Total mass of the system=3000+3000=6000 kg

acceleration a =100m/sec^2

Force needed to make this system move is given by

Thus 600,000 N force is needed to make this system move.

1.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it