A car's bumper is designed to withstand a 6.84 km/h (1.9 m/s) collision with an immovable object without damage to the body of the car. The bumper cushions the shock by absorbing the force over a distance. Calculate the magnitude of the average force (in N) on a bumper that collapses 0.270 m while bringing a 940 kg car to rest from an initial speed of 1.9 m/s. (Enter a number.) N

A car's bumper is designed to withstand a 6.84 km/h (1.9 m/s) collision with an immovable object without damage to the body of the car. The bumper cushions the shock by absorbing the force over a distance. Calculate the magnitude of the average force (in N) on a bumper that collapses 0.270 m while bringing a 940 kg car to rest from an initial speed of 1.9 m/s. (Enter a number.) N

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter6: Energy Of A System

Section: Chapter Questions

Problem 27P: A 6 000-kg freight car rolls along rails with negligible friction. The car is brought to rest by a...

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(a) A 75-kg man steps out a window and falls (from rest) 1.0 m to a sidewalk. What is his speed just before his feet strike the pavement? (b) If the man falls with his knees and ankles locked, the only cushion for his fall is an approximately 0.50-cm give in the pads of his feet. Calculate the average force exerted on him by the ground during this 0.50 cm of travel. This average force is sufficient to cause damage to cartilage in the joints or to break bones.
A 6 000-kg freight car rolls along rails with negligible friction. The car is brought to rest by a combination of two coiled springs as illustrated in Figure P6.27 (page 188). Both springs are described by Hookes law and have spring constants k1 = 1 600 N/m and k2, = 3 400 N/m. After the first spring compresses a distance of 30.0 cm, the second spring acts with the first to increase the force as additional compression occurs as shown in the graph. The car comes to rest 50.0 cm after first contacting the two-spring system. Find the cars initial speed.
Check Your Understanding There is a second solution to the system of equations solved in this example (because the energy equation is quadratic): v1.f=-2.5m/s , v2.f=0 . This solution is unacceptable on physical grounds; what’s with it?
A child of mass m starts from rest and slides without friction from a height h along a curved waterslide (Fig. P5.46). She is launched from a height h/5 into the pool. (a) Is mechanical energy conserved? Why? (b) Give the gravitational potential energy associated with the child and her kinetic energy in terms of mgh at the following positions: the top of the waterslide, the launching point, and the point where she lands in the pool. (c) Determine her initial speed V0 at the launch point in terms of g and h. (d) Determine her maximum airborne height ymax in terms of h, g, and the horizontal speed at that height, v0x. (e) Use the x-component of the answer to part (c) to eliminate from the answer to part (d), giving the height ymax in terms of g, h, and the launch angle . (f) Would your answers be the same if the waterslide were not frictionless? Explain. Figure P5.46
Some office workers use a sledgehammer to hit their broken computer and push it across an open field. If the computer has a mass of 5.2 kg and moves across the field with an initial velocity of 10.4 m/sec, how far will it travel before coming to a rest from friction (uopenfield = 0.45)?
a baseball catcher puts on an exhibition by catching a 0.15 kg ball, dropped from a helicopter at a height of 100m above the catcher. If the catcher "gives" with the ball for 0.75 m (was originally 1m off the ground) while catching it, what is the average force exerted on the mitt by the ball?
A sledgehammer of mass m = 1.9 kg falls freely vertically downward from a height of h = 2.5 m at an initial speed of v = 6.5 m/s before striking a partially buried piling. After the blow the piling has moved d = 0.075 m deeper. How much force, in newtons, was applied to the piling? Assume all the energy goes towards driving the piling into the ground, and the force of the sledgehammer is constant over the distance d that the piling is driven into the ground. Note that you can ignore the change in potential energy of the piling itself. Further, because d is so small compared to h, you can also ignore the change in potential energy of the hammer as well as it moves distance d.
A steel cube with a mass of 3.0 Kg is released from rest and slides down a ramp with an incline of 45.0 degrees, with a coeefficient of kinetic friciton of u = 0.328. How far will the block travel in 1.00 seconds.
a)Gayle runs at a speed of 3.80 m/s and dives on a sled, initially at rest on the top of a frictionless snow-covered hill. After she has descended a vertical distance of 5.00 m, her brother, who is initially at rest, hops on her back and together they continue down the hill. What is their speed at the bottom of the hill if the total vertical drop is 15.0 m? Gayle's mass is 49.5 kg, the sled has a mass of 5.50 kg and her brother has a mass of 30.0 kg.
The 78.5-kg swimmer in the figure starts a race with an initial velocity of 1.4 m/s and exerts an average force of 78.5 N backward with his arms during each 1.80 m long stroke. What is the subsequent average resistance force, in newtons, from the water during 5.25s it takes him to reach his top velocity of 2.55 m/s?
Assume that the force of a bow on an arrow behaves like the spring force. In aiming the arrow, an archer pulls the drawstring back 62 cm from its rest position and holds it in position with a force of 170 N. If the mass of the arrow is 59 g and the "spring" is massless, what is the speed (in m/s) of the arrow immediately after it leaves the bow?
A block of mass m=5.5kg slides on a rough surface and moves toward a spring with a spring constant k=1022N/m, as shown in the figure below. When the block is d=27.4m away from the spring, it has a velocity of v=14.8m/s. When the block momentarily stops, it has compressed the spring by x=16cm. What is the coefficient of kinetic friction between the block and the surface below? Provide your answer with two decimal places. Take g=9.80m/s2.