CM4: A 58 kg circus performer hangs from a bar suspended from a ceiling as shown in the figure. If the bar masses 12 kg (and its weight acts at its center) and has a length of 1.4 m, what is the tension T₂ in the rope? The rope is attached 0.85 m along the bar.

Figure CQ10.15 shows a side view of a childs tricycle with rubber tires on a horizontal concrete sidewalk. If a string were attached to the upper pedal on the far side and pulled forward horizontally, the tricycle would start to roll forward. (a) Instead, assume a siring is attached to the lower pedal on the near side and pulled forward horizontally as shown by A. Will the tricycle start to roll? If so, which way? Answer the same questions if (b) the string is pulled forward and upward as shown by B, (c) if the string is pulled straight down as shown by C, and (d) if the string is pulled forward and downward as shown by D. (e) What If? Suppose the string is instead attached to the rim of the front wheel and pulled upward and backward as shown by E. Which way does the tricycle roll? (f) Explain a pattern of reasoning, based on the figure, that makes it easy to answer questions such as these. What physical quantity must you evaluate? Figure CQ10.15

BIO The arm in Figure P10.35 weighs 41.5 N. The gravitational force on the arm acts through point A. Determine the magnitudes of the tension force F1 in the deltoid muscle and the force Fs exerted by the shoulder on the humerus (upper-arm bone) to hold the arm in the position shown. Figure P10.35

You have been hired as an expert witness in a case involving an injury in a factory. The attorney who hired you represents the injured worker. The worker was told to lift one end of a long, heavy crate that was lying horizontally on the floor and tilt it up so that it is standing on end. He began lifting the end of the crate, always applying a force that was perpendicular to the top of the crate. As the end of the crate got higher, at a certain angle, the bottom of the crate slipped on the floor, and the worker, in trying to recover, stepped forward and the crate landed on his foot, injuring it badly. As part of your investigation, you go to the factory and measure the coefficient of static friction between a crate and the smooth concrete floor. You find it to be 0.340. Prepare an argument for the attorney showing that it was impossible to lift the crate in the manner described without it slipping on the floor.

An object is being weighed using an unequal-arm balance (Fig. P14.76). When the object is in the left pan, a downward force of 3.0 N must be exerted on the right pan to balance the gravitational force on the object. When the object is in the right pan, a downward force of 2.0 N must be exerted on the left pan to balance the gravitational force on the object. Determine the magnitude of the gravitational force on the object. FIGURE P14.76

As shown in Figure OQ10.7, a cord is wrapped onto a cylindrical reel mounted on a fixed, friction less, horizontal axle. When does the reel have a greater magnitude of angular acceleration? (a) When the cord is pulled down with a constant force of 50 N. (b) When an object of weight 50 X is hung from the cord and released, (c) The angular accelerations in parts (a) and (b) are equal, (d) It is impossible to determine.

In one amusement park ride, riders enter a large vertical barrel and stand against the wall on its horizontal floor. The barrel is spun up and the floor drops away. Riders feel as if they are pinned to the wall by a force something like the gravitational force. This is a fictitious force sensed and used by the riders to explain events in the rotating frame of reference of the barrel. Explain in an inertial frame of reference (Earth is nearly one) what pins the riders to the wall, and identify all of the real forces acting on them.

A child of mass 40.0 kg is in a roller coaster car that travels in a loop of radius 7.00 m. At point A the speed of the car is 10.0 m/s, and at point B, the speed is 10.5 m/s. Assume the child is not holding on and does not wear a seat belt. (a) What is the force of the car seat on the child at point A? (b) What is the force of the car seat on the child at point B? (c) What minimum speed is required to keep the child in his seat at point A?

Unreasonable Results A mother pushes her child on a swing so that his speed is 9.00 m/s at the lowest point of his path. The swing is suspended 2.00 m above the child's center of mass. (a) What is the magnitude of the centripetal acceleration of the child at the low point? (b) What is the magnitude of the force the child exerts on the seat if his mass is 18.0 kg? (c) What is unreasonable about these results? (d) Which premises are unreasonable or inconsistent?

An iron bolt of mass 65.0 g hangs from a string 35.7 cm long. The top end of the string is fixed. Without touching it, a magnet attracts the bolt so that it remains stationary, but is displaced horizontally 28.0 cm to the tight from the previously vertical line of the string. The magnet is located to the right of the bolt and on the same vertical level as the bolt in the final configuration. (a) Draw a free-body diagram of the bolt. (b) Find the tension in the string, (c) Find the magnetic force on the bolt.