Concept explainers
Over the Christmas break, you are making some extra money for buying presents by working in a factory, helping to move crates around. At one particular time, you find that all the handtrucks, dollies, and carts are in use, so you must move a crate across the room a straight-line distance of 35.0 m without the assistance of these devices. You notice that the crate has a rope attached to the middle of one of its vertical faces. You decide to move the crate by pulling on the rope. The crate has a mass of 130 kg, and the coefficient of kinetic friction between the crate and the concrete floor is 0.350. (a) Determine the angle relative to the horizontal at which you should pull upward on the rope so that you can move the crate over the desired distance with the force of the smallest magnitude. (b) At this angle of pulling on the rope, how much work do you do in dragging the crate over the desired distanced?
Trending nowThis is a popular solution!
Chapter 7 Solutions
Physics for Scientists and Engineers with Modern Physics
- If the car's speed were not reduced by any structural effects or by friction, how long would it take to complete the race? What is the speed of the car at the end of the race?arrow_forwardA 10 kg box is being pushed across a rough surface with a constant speed of 2 m/s. The person pushing the box slips and stops pushing. The box continues to slide across the surface before coming to rest. If the coefficient of friction between the crate and the surface is 0.1, how far does the box travel before coming to rest?arrow_forwardAn airplane of mass 3.60 × 105 kg experienced a problem with all its tires when it was about to touch down at a runway of an airport. The tires were deadlocked and not able to roll. The airplane began to skid once it touched down and left behind a 728 m long skid mark on the runway before it came to a stop. Even though everyone on the airplane was safe, the pilot was accused of failing to land the airplane within the allowable speed limit of 80.0 m/s and his pilot license was suspended. Given that the coefficient of kinetic friction between the tires and runway was 0.496. (i) Determine the work done by friction on the tires.(ii) Use the Work-Energy Theorem to evaluate if the suspension of the pilot’s license should be revoked. #This is an exercise question, please help. Thank You.arrow_forward
- The figure shows a 2400 kg cable car descending a high hill. A counterweight of mass 2200 kg on the other side of the hill aids the brakes in controlling the cable car's speed. The rolling friction of both the cable car and the counterweight are negligible. How much braking force does the cable car need to descend at constant speed? Counterweight 200 m 30° 20° 2200 N 3300 N 980 N 4400 Narrow_forwardA marble rolls off the roof of Physics hall and falls vertically. Just before it reaches the ground, the marble's speed is 15 m/s. Neglect air resistance and determine the height of Physics Hall. 8.7 m 11.5 m 16 m 13 marrow_forwardThe 2013 women’s pole vault World Record of 4.89 m belongs to Yelena Isinbayeva of Russia. If the pole vault mat has the dimensions of 6.0 m×8.0 m×0.8 m , what is the vertical speed of the vaulter right before she strikes the mat?arrow_forward
- Carol wants to move her 32kg sofa to a different room in the house. She places "sofa disks", slippery disks with mu k =.080 , on the carpet, under the feet of the sofa. She then pushes the sofa at a steady.4 .4 m/s across the floor. How much force does she apply to the sofa?arrow_forwardA ball with a unknown mass is attached to a cable and suspended from the ceiling. The distance from the ceiling to the hanging is 1.9 m (the length of the cable). A person pulls the ball so the cable makes an angle of 64 degrees to the vertical. Determine the maximum speed that can be reached by the mass (in m/s).arrow_forwardThe 2090 kg cable car shown in the figure descends a 200-m-high hill. In addition to its brakes, the cable car controls its speed by pulling an 1860 kgcounterweight up the other side of the hill. The rolling friction of both the cable car and the counterweight are negligible. How much braking force does the cable car need to descend at constant speed? One day the brakes fail just as the cable car leaves the top on its downward journey. What is the runaway car's speed at the bottom of the hill?arrow_forward
- A cart for hauling ore out of a gold mine has a mass of 429 kg, including its load. The cart runs along a straight stretch of track that climbs a shallow 4.33° incline. A donkey, which is trudging along and to the side of the track, has the unenviable job of pulling the cart up the slope with a 399 N force for a distance of 113 m by means of a rope that is parallel to the slope but makes an angle of 15.1° with the track. The coefficient of friction for the cart's wheels on the track is 0.0161 Use g=9.81 m/s^2, and note that angle A in the image is the angle of the incline while angle B is the angle the rope makes with the track. Find the work ?dthat the donkey performs on the cart during this process. Find the work ?g that the force of gravity performs on the cart during this process. Calculate the work ?f done on the cart by friction during this process.arrow_forwardYou are working as a delivery person for a dairy store. In the back of your pickup truck is a crate of eggs. The dairy company has run out of bungee cords, so the crate is not tied down. You have been told to drive carefully because the coefficient of static friction between the crate and the bed of the truck is 0.600. You are not worried, because you are traveling on a road that appears perfectly straight. Due to your confidence and inattention, your speed has crept upward to 46.6 mi/h. Suddenly, you see a curve ahead with a warning sign saying, "Danger: unbanked curve with radius of curvature 35.0 m." You are 15.0 m from the beginning of the curve. What can you do to save the eggs?arrow_forwardSame type of track as in the previous problem, this time with d = 2.73 m. The block starts at x = 0, and is given a push to the left with an initial speed of 4.46 m/s, so it starts sliding up the track to the left. At what value of x will the block reverse direction and start sliding back down? y = (x^2) /d for x<0 and by y = -(x^2)/d for x>0 1.66 m 1.01 m -1.01 m -1.66 marrow_forward
- Glencoe Physics: Principles and Problems, Student...PhysicsISBN:9780078807213Author:Paul W. ZitzewitzPublisher:Glencoe/McGraw-Hill