3.2.2 Solving Problems Using Newton's Laws: Ropes and Tension

Question 1

Solving Problems Using Newton’s Laws: Ropes and Tension

Answer 1

• Tension is a stretching or straining force, for example, the force applied to a rope.
• An ideal rope doesn’t stretch, can only pull, and is massless.
• If a rope is massless, the net force on it is zero. The force on one end of the rope is equal in magnitude and opposite indirection to the force on the other end of the rope.
• Pulleys change the direction, but not the magnitude, of forces on ropes.

Question 2

The diagram shows two carts attached by a string threaded through a frictionless pulley. Which of the following is the equation for the acceleration of the carts?

Answer 2

a = M2/(M1 + M2) (g)

Question 3

The attached diagram shows two fingers pulling on opposite ends of a rope.

The force of the rope on one finger is equal in magnitude and opposite in direction to the force of the rope on the other finger. Which of the following equations correctly measures the result?

Answer 3

Fnet = F + (−F)

Question 4

Which of the following does not describe a quality of the ideal rope as an instrument of force?

Answer 4

It has a consistent width.

Question 5

The attached diagram shows two weights attached by a string going around a pulley.

The force of gravity is shown in the diagram as W. Assume there is no friction and an ideal rope is used. Weight M1 is very heavy and weight M2 is very light. Which of the following correctly describes what will happen in this system?

Answer 5

Because a net force (W) is being applied to the system, M2 will accelerate downward and, because of the tension in the rope, M1 will accelerate to the right at the same time

Question 6

The attached force diagram shows a weight hanging by a rope.

The object is moving upward with a constant velocity. T equals the tension in the rope. The arrow indicates the positive component of the vector. Which of the following equations related to this experiment is not correct?

Answer 6

T + mg = Fnet

Question 7

The diagram shows two carts attached by a rope going through a frictionless pulley. With respect to the diagram, which of the following is not correct?

Answer 7

T = −M 2g

Question 8

The diagram shows two carts attached by a string that is threaded through a frictionless pulley. A net force, W, is being applied to the system. Which of the following equations for determining the value of T is correct?

Answer 8

T − M 2g = −M 2a

Question 9

The diagram shows two carts attached by a string that is threaded through a frictionless pulley. A net force, W, is being applied to the system. Which of the following equations for determining the value of T is correct?

Answer 9

T = M 1a

Question 10

Consider a rope with a mass hanging from it. The upward force holding this mass up is provided by the rope’s __________________.

Answer 10

tension