An uncontrolled 850 kg car strikes squarely a motorway crash cushion in which the car is brought to rest by successively crushing steel barrels. The length of the crash cushion is 5.9 m, and the magnitude Fof the force required to crush the barrels as a function of the distance a the car has moved into the cushion is given by 85KN (0 < x < 1.7m) (1.7 < r < 4.4m) (4.4 < a < 5.9m) 130kN 170kN a) Determine an expression for the work done by the force F as a function of x. b) If the car strikes the crash cushion with a velocity of 138 km/h, determine the distance the car will move into the cushion before it comes to rest and the maximum deceleration of the car.

An uncontrolled 850 kg car strikes squarely a motorway crash cushion in which the car is brought to rest by successively crushing steel barrels. The length of the crash cushion is 5.9 m, and the magnitude Fof the force required to crush the barrels as a function of the distance a the car has moved into the cushion is given by 85KN (0 < x < 1.7m) (1.7 < r < 4.4m) (4.4 < a < 5.9m) 130kN 170kN a) Determine an expression for the work done by the force F as a function of x. b) If the car strikes the crash cushion with a velocity of 138 km/h, determine the distance the car will move into the cushion before it comes to rest and the maximum deceleration of the car.

International Edition---engineering Mechanics: Statics, 4th Edition

4th Edition

ISBN:9781305501607

Author:Andrew Pytel And Jaan Kiusalaas

Publisher:Andrew Pytel And Jaan Kiusalaas

Chapter7: Dry Friction

Section: Chapter Questions

Problem 7.79P: The coefficient of rolling resistance between the 30-kg lawn roller and the ground is r=0.1. (a)...

See similar textbooks

Similar questions

The 650-kg hammer of a drop-hammer pile driver falls from a height of 1.2 m onto the top of a 140-kg pile, driving it 110 mm into the ground. Assuming perfectly plastic impact (e= 0), determine the average resistance of the ground to penetration.
A 2600-lb car is moving at a speed of 66 mph when the brakes are fully applied, causing all four wheels to skid. Determine the time required to stop the automobile on a rough road, where the coefficient of kinetic friction is equal to 0.60.
Activity 3. A body that weighs W Newtons falls from rest from a height of 600mm and strikes a spring whose scale is 7.00 N/mm. If the maximum compression of the spring is 150 mm, what is the value of W? Disregard the mass of the spring.
For a technology project, a student has built a vehicle, of total mass 6.00 kg, that moves itself. As shown, it runs on four light wheels. A reel is attached to one of the axles, and a cord originally wound on the reel goes up over a pulley attached to the vehicle to support an elevated load. After the vehicle is released from rest, the load descends very slowly, unwinding the cord to turn the axle and make the vehicle move forward (to the left as shown). Friction is negligible in the pulley and axle bearings. The wheels do not slip on the floor. The reel has been constructed with a conical shape so that the load descends at a constant low speed while the vehicle moves horizontally across the floor with constant acceleration, reaching a final velocity of 3.00î m/s. (a) Does the floor impart impulse to the vehicle? If so, how much? (b) Does the floor do work on the vehicle? If so, how much? (c) Does it make sense to say that the final momentum of the vehicle came from the floor? If…
In the system shown two blocks A and B are joined by anegligible ground cable passing through a fixed pulley that does notbroken. Block A has a mass of 45 kg and the coefficients ofstatic friction are 0.40 between rope and pulley and 0.30 betweenblocks and inclined planes. Determine: a) The maximum mass of block B that will cause theblock A slides down.b) The minimum mass of block B that will cause block A to slide up.c) Explain the condition of the system if the mass of block B were 80 kg.
Block B is on top of an inclined plane and is being supported by Rod AB, which is attached to Block A. The weight of Block A is 40 KN, and the weight of Block B is 80 KN. Force F prevents the block from sliding. Determine the Normal Force N of the surface that supports Block A. Neglect all friction.
Block A has a mass mA and is attached to a spring having a stiffness k and unstretched length l0. If another block B, having a mass mB, is pressed against A so that the spring deforms a distance d, show that for separation to occur it is necessary that d > 2µkg(mA + mB )/k, where µkis the coefficient of kinetic friction between the blocks and the ground. Also, what is the distance the blocks slide on the surface before they separate?
The 2-Mg truck is traveling at 15 m/s when the brakes on all its wheels are applied, causing it to skid for a distance of 10 m before coming to rest. (Figure 1) Part A: Determine the constant horizontal force developed in the coupling C during this time. The total mass of the boat and trailer is 1 Mg. Express your answer to three significant figures and include the appropriate units. Part B:
A block weighing 96.6 lb is dropped from a height of 4 ft upon a spring whose modulus is 100 lb per in. What velocity will the block have at the instant the spring is deformed in 4 in.?
A physics student of mass 43.0 kg is standing at the edge of theflat roof of a building, 12.0 m above the sidewalk. An unfriendly dog isrunning across the roof toward her. Next to her is a large wheel mountedon a horizontal axle at its center. The wheel, used to lift objects from theground to the roof, has a light crank attached to it and a light rope wrappedaround it; the free end of the rope hangs over the edge of the roof. Thestudent grabs the end of the rope and steps off the roof. If the wheel hasradius 0.300 m and a moment of inertia of 9.60 kg . m2 for rotation aboutthe axle, how long does it take her to reach the sidewalk, and how fast willshe be moving just before she lands? Ignore friction in the axle.
Q.1) A 50 kg block is dropped from a height of 2 m onto the the 20 kg pan of a spring scale.Assuming the impact to be perfectly plastic, determine the maximum deflection of the pan.The constant of the spring is k = 20 kN/m.Q.2) Answer the following questions:a) Why does any person lean towards right while carrying a bag in her left hand?b) Give the physical significance of moment of inertia.c) Two satellites of equal masses, which can be considered as particles areorbiting the earth at different heights? Will their moments of inertia be same ordifferent?Q.3) A 5-kg model rocket is launched vertically and reaches an altitude of 100 m with a speedof 40 m/s at the end of powered flight, time t=5 s. As the rocket approaches its maximumaltitude it explodes into two parts of masses mA=1.7 kg and mB=3.3 kg. Part A is observed tostrike the ground 50 m west of the launch point at t=6 s. Determine the position of part B atthat time.
The design for a new cementless hip implant is to be studied using an instrumented implant and a fixed simulated femur. Assuming the punch applies an average force of 2 kN over a time of 2 ms to the 200-g implant, determine (a) the velocity of the implant immediately after impact, (b) the average resistance of the implant to penetration if the implant moves 1 mm before coming to rest.