Concept explainers
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
- According to a simplified model of a mammalian heart, at each pulse approximately 20 g of blood is accelerated from 0.25 m/s to 0.35 m/s during a period of 0.10 s. What is the magnitude of the force exerted by the heart muscle?arrow_forwardA 1.2 kg ball is falling in the -y direction at a speed of 25 m/s. The ball strikes the floor and then rebounds with a speed of 10 m/s. If the ball is in contact with the floor for 0.02 seconds, what is the magnitude of the average force of the floor acting on the ball? Group of answer choices 1500 N 900 N 600 N 2100 N 200 N 0 Narrow_forwardTwo skydivers are holding on to each other while falling straight down at a common terminal speed of 53.50 m/s. Suddenly they push away from each other. Immediately after separation the first skydiver who has a mass of 83.80 kg has the following velocity components ( with straight down corresponding to the positive z axis). V1x= 5.430 m/s v1y= 4.750 m/s v1z= 53.50m/s. What are the x and y components of the velocity of the second skydiver whose mass is 63.20 kg immediately after separation. What is the change in kinetic energy of the system?arrow_forward
- In the very Dutch sport of Fierljeppen, athletes run up to a long pole and then use it to vault across a canal. At the very top of his arc, a 55 kg vaulter is moving at 2.5 m/s and is 5.1 m from the bottom end of the pole. What vertical force does the pole exert on the vaulter?arrow_forwardA Wall of Death is a carnival show featuring a motorcyclist rides along the vertical wall of the cylinder and performs various stunts while doing so. Given that the radius of the cylinder is 7 m and the static coefficient of friction is 0.8, what is the minimum speed in m/s2 that the motorcyclist must do to prevent the motorcycle to slip from the wall?arrow_forwardA hockey puck with a mass of 0.170 kg moving in a straight line at 1.5 m / s collides with an identical puck that is at rest. As a result, the first disk deviates an angle of 30 ° from its original path and continues to move with a speed of 2.9 m / s. What is the magnitude of the final velocity of the second disk?arrow_forward
- Three forces act on an object, considered to be a particle, which moves with constant velocity v =(3 m/s)î +(−2 m/s)ĵ Two of the forces are shown in the picture below., while the third force, F_3 is not given. 1.) What are the x, y, and z components of F_3?arrow_forwardA 6100 kg rocket is set for vertical firing from the ground. If the exhaust speed is 1200 m/s, how much gas must be ejected each second if the thrust (a) is to equal the magnitude of the gravitational force on the rocket and (b) is to give the rocket an initial upward acceleration of 21 m/s2?arrow_forwardA rocket has a total mass of 1.17 105 kg and a burnout mass of 1.03 104 kg, including engines, shell and payload. The rocket blasts off from Earth and exhausts all its fuel in 4.17 min, burning the fuel at a steady rate with an exhaust velocity of ve= 4.89 103 m/s. (a) If air friction and gravity are neglected, what is the speed of the rocket at burnout? (b) What thrust does the engine develop at liftoff? (c) What is the initial acceleration of the rocket if gravity is not neglected?arrow_forward
- In the figure, a body with a mass of 2 kg moves under the influence of two constant forces F1 = 5N and F2 = 4N in the xy plane. At time t = 0, the object is at point 0 and its speed is V = 2i + j (m / s). What is the acceleration of the particle and its position after 2 seconds in terms of the unit vector?arrow_forwardStarting from rest, a 57.0 kg woman jumps down to the floor from a height of 0.800 m, and immediately jumps back up into the air. While she is in contact with the ground during the time interval 0 < t < 0.800 s, the force she exerts on the floor can be modeled using the functionarrow_forwardConsider the Atwood machine shown in the figure, where m1 = 2.00 kg and m2 = 5.00 kg. The system starts at rest, then the sphere is given a quick push downward, giving it an initial speed of 2.45 m/s. Assume the pulley and cord are massless, and the cord is inextensible. Neglect friction. (a)Through what distance (in m) will m1 descend? b)What is the velocity (in m/s) of m1 after 1.80 s? magnitudearrow_forward
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