2. John pulls a box weighing w = 105 N up a = 22.0° incline, as shown in the fig

Question

2. John pulls a box weighing w = 105 N up a = 22.0° incline, as shown in the figure. The friction between John and the incline is enough to prevent him from sliding. There is also some friction between the floor and the box. Make a free-body diagram of the box and John. Check your answer with the solution posted on OWL.
Assuming the coefficient of kinetic friction between the floor and the box is µk = 0.120, and John pulls with force F = 263 N, calculate the magnitude of the acceleration of the box.

3. What is the minimum coefficient of static friction required to prevent John from slipping if he has a mass of 73 kg?

4. On her flight home at Thanksgiving, Margaret decides to apply the physics she has learned in PHYC1300 to measure the speed of the aircraft when it takes off. She dangles her watch from a string while the aircraft accelerates down the runway. Draw a free body diagram of the watch. Using her protractor, she notices that the string makes an angle of 28° with respect to the vertical edge of the window as the aircraft accelerates on the runway, which takes about 20 s. Estimate the takeoff speed of the aircraft.

5. In a rescue, a 80.1 kg police officer is suspended by two cables, as shown in the figure. Cable A makes an angle A = 28.0° with respect to the horizontal, and cable B, B = 54.0°. Sketch a free body diagram. Calculate the tension in cable A.

6. At the zoo, two monkeys weighing 24.0 N each are playing on a rope-and-pulley system. If the lower rope is attached to a weight of mass m = 13.0 kg, what is the tension in the lower rope at point A, assuming the system is in equilibrium?

7. What is the tension in the upper rope at point B ?

8. The diagram of the leg shows the femur (1) and tibia (2). The quadriceps muscle (3) applies a force to the lower leg via a tendon (4) that is embedded with the kneecap (5). If the force applied by the muscle to the tendon is FM = 500 N, what is the force of the femur on the kneecap, if the leg is in equilibrium? A simplified model of the leg is shown next to the diagram. The leg bones are represented by two beams attached by a pin. The tendon is modelled by a rope and the kneecap acts like a pulley. The tendon above the kneecap makes an angle 1 = 66° with respect to the vertical, and the portion of the tendon below the kneecap makes an angle of 2 = 39° with respect to the vertical. Enter the x component, followed by the y component.

9. A car race is taking place on the track shown. All the cars are moving at constant speeds. The cars are on curved segments of the track, except for the car at point F. The car at point A has velocity vA, the car at B, vB, etc. Select all the statements that are true, e.g., ABC. If none are correct, enter N.

The acceleration of the car at point A is parallel to vA.

The acceleration of the car at point B is perpendicular to vB and directed toward the inside of the track.

The track is equally curved at point A and point E. If the car at point A has twice the speed of the car at point E, its acceleration is the same as that of the car at point E.

The acceleration of the car at point D is parallel to vD.

The acceleration of the car at point C is perpendicular to vC and directed toward the outside of the track.

If all cars have equal speeds, the acceleration of car B is largest.

10. A popular ride at amusement parks is shown in the figure.
In this ride, people sit in a swing that is suspended from a long, rotating arm. Riders are at a distance of x = 12.1 m from the axis of rotation and move with a speed of 43.5 km/h. Calculate the centripetal acceleration of the riders.

11. Calculate the angle the supporting wires make with the vertical

Explanation / Answer

multiple questions allowed to solve 1 question at a time:

question 6) At the zoo, two monkeys weighing 24.0 N each are playing on a rope-and-pulley system. If the lower rope is attached to a weight of mass m = 13.0 kg, what is the tension in the lower rope at point A, assuming the system is in equilibrium?

answer)

At A, T = mg = 13kg * 9.8m/s² = 127.4 N

At B, T = 2 * 127.4N + 24N = 278.8 N

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