You have been hired as an expert witness in a court caseinvolving an automobile accident. The accident involvedcar A of mass 1500 kg which crashed into stationary car Bof mass 1100 kg. The driver of car A applied his brakes15 m before he skidded and crashed into car B. After thecollision, car A slid 18 m while car B slid 30 m. The coefficient of kinetic friction between the locked wheels and the road was measured to be 0.60. Show that the driver of car A was exceeding the 55 mi/h (90km/h) speed limit before applying the brakes.

You have been hired as an expert witness in a court caseinvolving an automobile accident. The accident involvedcar A of mass 1500 kg which crashed into stationary car Bof mass 1100 kg. The driver of car A applied his brakes15 m before he skidded and crashed into car B. After thecollision, car A slid 18 m while car B slid 30 m. The coefficient of kinetic friction between the locked wheels and the road was measured to be 0.60. Show that the driver of car A was exceeding the 55 mi/h (90km/h) speed limit before applying the brakes.

University Physics Volume 1

18th Edition

ISBN:9781938168277

Author:William Moebs, Samuel J. Ling, Jeff Sanny

Publisher:William Moebs, Samuel J. Ling, Jeff Sanny

Chapter5: Newton's Law Of Motion

Section: Chapter Questions

Problem 49P: A baseball catcher is performing a stunt for a television commercial. He will catch a baseball (mass...

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A baseball catcher is performing a stunt for a television commercial. He will catch a baseball (mass 145 g) dropped from a height of 60.0 m above his glove. His glove stops the ball in 0.0100 s. What is the force exerted by his glove on the ball?
A young girl is riding a bicycle that has a total mass (including the kid) of 21.2 kg. The girl is moving at 5.99 m/s on a flat road when suddenly she slams on the brakes and skids to a stop in 8.22 meters. What was the magnitutde of the average force due to friction acting on the bicycle? Remeber, the magnitude of a force is always positive. Assume a constant friction force measured in Newtons and 3 significant digits in your answer.
As a fish jumps vertically out of the water, assume thatonly two significant forces act on it: an upward force F exertedby the tail fin and the downward force due to gravity. A recordChinook salmon has a length of 1.50 m and a mass of 61.0 kg.If this fish is moving upward at 3.00 m/s as its head first breaksthe surface and has an upward speed of 6.00 m/s after twothirdsof its length has left the surface, assume constant accelerationand determine (a) the salmon’s acceleration and (b)the magnitude of the force F during this interval.
As a protest against the umpire’s calls, a baseball pitcherthrows a ball straight up into the air at a speed of 20.0 m/s. Inthe process, he moves his hand through a distance of 1.50 m.If the ball has a mass of 0.150 kg, find the force he exerts onthe ball to give it this upward speed.
A 2 000-kg car is slowed down uniformly from 20.0 m/s to 5.00 m/s in 4.00 s. (a) What average force acted on the car during that time, and (b) how far did the car travel during that time?
A person in a kayak starts paddling, and it accelerates from 0 to 0.8 mile/hour in adistance of 0.8km. If the combined mass of the person and the kayak is 80kg, whatis the magnitude of the net force acting on the kayak?
A car moving at 14 m/s crashes into a tree and stops in 0.91 s. The mass of the passenger inside is 69 kg. Calculate the magnitude of the average force, in newtons, that the seat belt exerts on the passenger in the car to bring him to a halt.
A light train made of two cars travels at 72 km/h. The mass of car Ais 18 Mg and the mass of car 8is 13 Mg. When the brakes are suddenly apolied, a constant braking force of 19 kN is applied to each car. Determine (a) the time required for the train to stop after the brakes are applied, (5) the force in the coupling between the cars while the train is slowing down.
A freight train consists of two 8.00×104-kg enginesand 45 cars with average masses of 5.50×104kg . (a) What force must each engine exert backward on the track toaccelerate the train at a rate of 5.00×10–2 m/s2if the force of friction is 7.50×105 N , assuming the engines exertidentical forces? This is not a large frictional force for such amassive system. Rolling friction for trains is small, andconsequently trains are very energy-efficient transportationsystems. (b) What is the force in the coupling between the37th and 38th cars (this is the force each exerts on the other),assuming all cars have the same mass and that friction isevenly distributed among all of the cars and engines?
A constant horizontal force of 37 N pushes a 20 kg mass through a medium that resists its motion with .9 N for every meter per second of speed. The initial velocity of the mass is 7 meters per second in the direction opposite of the applied force. Find the velocity of the mass after 25 seconds.
In 1991, a lobster with a mass of 20.0 kg was caught off the coast of Nova Scotia, Canada.Imagine this lobster involved in a friendly tug of war with several smaller lobsters on ahorizontal plane at the bottom of the sea. Suppose the smaller lobsters are able to drag thelarge lobster, so that after the large lobster has been moved 1.55 m its speed is 0.550 m/s. Ifthe lobster is initially at rest, what is the magnitude of the net force applied to it by thesmaller lobsters? Assume that friction and resistance due to moving through water arenegligible
Paleontologists estimate that if a Tyrannosaurus rex had tripped and fallen, the ground would have exerted anormal force of approximately 260,000 N on its torso as it landed.Assuming the torso has a mass of 3800 kg, (a) find the magnitudeof the torso’s upward acceleration as it comes to rest. (For comparison, humans lose consciousness with an acceleration of about 7g.)(b) Assuming the torso of a T. rex is in free fall for a distance of 1.46m as it falls to the ground, how much time is required for the torsoto come to rest once it contacts the ground?