6. Intro to Forces (Dynamics)

Three identical boxes A, B, and C rest on horizontal surfaces. Box A is on a flat table, box B is on the same table with an additional weight placed on top, and box C is on the same table with someone pulling upward on it with a rope (but not lifting it off the table). Rank the boxes in order of the magnitude of the normal force acting on them, from greatest to least.

It takes the elevator in a skyscraper 4.0 s to reach its cruising speed of 10 m/s. A 60 kg passenger gets aboard on the ground floor. What is the passenger's weight before the elevator starts moving?

Two $25.0$-N weights are suspended at opposite ends of a rope that passes over a light, frictionless pulley. The pulley is attached to a chain from the ceiling. What is the tension in the rope?

(II) What will a spring scale read for the weight of a 58.0‑kg woman in an elevator that moves with a downward acceleration 0.18 g?

A 50 kg box hangs from a rope. What is the tension in the rope if: The box moves up at a steady 5.0 m/s?

FIGURE EX6.19 shows the velocity graph of a 75 kg passenger in an elevator. What is the passenger's weight at t=1s? At 5 s? At 9 s?

A 3-kg bucket is being pulled upwards by a cord. The tension in the cord is 35 N. What is the acceleration of the bucket? (The mass of the cord is negligible, which means you can assume m_cord = 0.)

A 6750-kg helicopter accelerates upward at 0.80m/s² while lifting a 1080-kg frame at a construction site, Fig. 4–66.

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(c) What force does the cable exert on the helicopter?

(II) How much tension must a cable withstand if it is used to accelerate a 1400-kg car vertically upward at 0.70m/s²?

(II) A narrow but solid spool of thread has radius R and mass M. If you pull up on the thread so that the cm of the spool remains suspended in the air at the same place as it unwinds, what force must you exert on the thread?

A light rope is attached to a block with mass $4.00$ kg that rests on a frictionless, horizontal surface. The horizontal rope passes over a frictionless, massless pulley, and a block with mass m is suspended from the other end. When the blocks are released, the tension in the rope is $15.0$ N. Find $m$.

(III) An object moving vertically has $\(\overrightarrow{\mathbf{v}\)}_{}=\(\overrightarrow{\mathbf{v}\)}_0$ at t = 0. Determine a formula for its velocity as a function of time assuming a resistive force F = -bv as well as gravity for two cases: $\(\overrightarrow{\mathbf{v}\)}_0$ is downward.

The Mars Rover Perseverance weighed about 10,000 N while on Earth. After it reached the surface of Mars, it weighed about 3790 N. What is the gravitational acceleration on Mars?

A 50 kg box hangs from a rope. What is the tension in the rope if: The box has v_y = 5.0 m/s and is speeding up at 5.0 m/s²