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You have been called as an expert witness for a trial in which a driver has been charged with speeding but is claiming innocence. He claims to have slammed on his brakes to avoid rear-ending another car, but tapped the back of the other car just as he came to rest. You have been hired by the prosecution to prove that the driver was indeed speeding. You have received data as follows from the police: Skid marks left by the driver are 56.0 m long and the roadway is level. Tires matching those on the car of the driver have been dragged over the same roadway to determine that the coefficient of kinetic friction between the tires and the roadway is 0.82 at all points along the skid mark. The speed limit on the road is 35 mi/h. Construct an argument to be used in court to show that the driver was indeed speeding.
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Chapter 5 Solutions
Physics for Scientists and Engineers
- A robot with fancy wheels is trained to move in two directions simultaneously. The force in the forward direction is 10 N and the force in the horizontal direction is 8 N. If the robot starts from rest, has a mass of 75 kg and travels for 100 seconds, what is the magnitude of the robot's final displacement?arrow_forwardYour answer is partially correct. In a two-dimensional tug-of-war, Alex, Betty, and Charles pull horizontally on an automobile tire at the angles shown in the picture. The tire remains stationary in spite of the three pulls. Alex pulls with force F A of magnitude 205 N, and Charles pulls with force F c of magnitude 184 N. Note that the direction of F c is not given. What is the magnitude of Betty's force F B if Charles pulls in (a) the direction drawn in the picture or (b) the other possible direction for equilibrium? Alex Charles 144° Betty (a) Number 304.72 Units N (b) Number 49.1 Unitsarrow_forwardYou are pushing a rubber crate against a concrete floor. The two surfaces have a static coefficient of friction of 0.61 and a kinetic coefficient of friction of 0.49. The floor is horizontal, and the crate has a mass of 25.0 kg, and is initially at rest. You are pushing with a horizontal force of 100 N. What is the magnitude of the force of friction in this case? Give your answer in units of N, to three significant figures.arrow_forward
- Two forces F, = (55.76î - 12.93ĵ) N and F, = (27.41î – 72.94ĵ) N are exerted on a particle. The particle's mass is 10.14 kg. %3D (a) Find the particle's acceleration in component form. (Express your answer in vector form.) a = m/s? (b) What are the magnitude and direction of the acceleration? magnitude m/s2 direction ° counterclockwise from the +x axisarrow_forwardYou are pushing a rubber crate against a concrete floor. The two surfaces have a static coefficient of friction of 0.66 and a kinetic coefficient of friction of 0.52. The floor is horizontal, and the crate has a mass of 25.0 kg, and is initially at rest. You are pushing with a horizontal force of 85 N. What is the magnitude of the force of friction in this case? Give your answer in units of N, to three significant figures. You are pushing a wooden crate against a rubber floor. The two surfaces have a static coefficient of friction of 0.54 and a kinetic coefficient of friction of 0.42. The floor is horizontal, and the crate has a mass of 25.0 kg, and is initially at rest. You are pushing with a horizontal force of 135 N. What is the magnitude of the force of friction in this case? Give your answer in units of N, to three significant figures.arrow_forwardHand-written, step-by-step solution, please. Thank u!arrow_forward
- The high-speed winds around a tornado can drive projectiles into trees, building walls, and even metal traffic signs. In a laboratory simulation, a standard wood toothpick was shot by pneumatic gun into an oak branch. The toothpick mass was 0.15 g, its speed before entering the branch was 212 m/s, and its penetration depth was 17 mm. If its speed was decreased at a uniform rate, what was the magnitude of the force of the branch on the toothpick? Number Unitsarrow_forwardYou are pushing a wooden crate against a rubber floor. The two surfaces have a static coefficient of friction of 0.45 and a kinetic coefficient of friction of 0.38. The floor is horizontal, and the crate has a mass of 25.0 kg, and is initially at rest. You are pushing with a horizontal force of 155 N. What is the magnitude of the force of friction in this case? Give your answer in units of N, to three significant figures.arrow_forwardConsider an object on an incline where friction is present. The angle between the incline and the horizontal is θ and the coefficient of kinetic friction is μk. Find an expression for the acceleration of this object. Treat down the incline as the positive direction. Calculate the acceleration, in meters per second squared, of this object if θ = 31° and μk = 0.31. Treat down the incline as the positive direction.arrow_forward
- A 1.4 gram bullet is shot into a tree stump. It enters at a velocity of 341 m/sec and comes to rest after having penetrated the stump in a straight line. It takes 0.00032 sec to come to a stop after striking the stump. What was the force on the bullet during impact? (answer in Newtons)arrow_forwardNeeds Complete typed solution with 100 % accuracy.arrow_forwardIn a two-dimensional tug-of-war, Alex, Betty, and Charles pull horizontally on an automobile tire at the angles shown in the picture. The tire remains stationary in spite of the three pulls. Alex pulls with force É A of magnitude 222 N, and Charles pulls with force magnitude 188 N. Note that the direction of F c is not given. What is the magnitude of Betty's force F B if Charles pulls in (a) the c of direction drawn in the picture or (b) the other possible direction for equilibrium? Alex Charles 140° Betty (a) Number i Units (b) Number i Unitsarrow_forward
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