Chapter 7: Problem 16
Using momentum and force principles, explain why an air bag reduces injury in an automobile collision.
Chapter 7: Problem 16
Using momentum and force principles, explain why an air bag reduces injury in an automobile collision.
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Get started for freeAssume the nucleus of a radon atom, \({ }^{222} \mathrm{Rn}\), has a mass of \(3.68 \cdot 10^{-25} \mathrm{~kg} .\) This radioactive nucleus decays by emitting an alpha particle with an energy of \(8.79 \cdot 10^{-13} \mathrm{~J}\). The mass of an alpha particle is \(6.65 \cdot 10^{-27} \mathrm{~kg}\). Assuming that the radon nucleus was initially at rest, what is the velocity of the nucleus that remains after the decay?
During an ice-skating extravaganza, Robin Hood on Ice, a 50.0 -kg archer is standing still on ice skates. Assume that the friction between the ice skates and the ice is negligible. The archer shoots a \(0.100-\mathrm{kg}\) arrow horizontally at a speed of \(95.0 \mathrm{~m} / \mathrm{s} .\) At what speed does the archer recoil?
When a \(99.5-\mathrm{g}\) slice of bread is inserted into a toaster, the toaster's ejection spring is compressed by \(7.50 \mathrm{~cm}\). When the toaster ejects the toasted slice, the slice reaches a height \(3.0 \mathrm{~cm}\) above its starting position. What is the average force that the ejection spring exerts on the toast? What is the time over which the ejection spring pushes on the toast?
An uncovered hopper car from a freight train rolls without friction or air resistance along a level track at a constant speed of \(6.70 \mathrm{~m} / \mathrm{s}\) in the positive \(x\) -direction. The mass of the car is \(1.18 \cdot 10^{5} \mathrm{~kg}\). a) As the car rolls, a monsoon rainstorm begins, and the car begins to collect water in its hopper (see the figure). What is the speed of the car after \(1.62 \cdot 10^{4} \mathrm{~kg}\) of water collects in the car's hopper? Assume that the rain is falling vertically in the negative \(y\) -direction. b) The rain stops, and a valve at the bottom of the hopper is opened to release the water. The speed of the car when the valve is opened is again \(6.70 \mathrm{~m} / \mathrm{s}\) in the positive \(x\) -direction (see the figure). The water drains out vertically in the negative \(y\) -direction. What is the speed of the car after all the water has drained out?
Which of the following statements about car collisions are true and which are false? a) The essential safety benefit of crumple zones (parts of the front of a car designed to receive maximum deformation during a head-on collision) results from absorbing kinetic energy, converting it into deformation, and lengthening the effective collision time, thus reducing the average force experienced by the driver. b) If car 1 has mass \(m\) and speed \(v\), and car 2 has mass \(0.5 m\) and speed \(1.5 v\), then both cars have the same momentum. c) If two identical cars with identical speeds collide head on, the magnitude of the impulse received by each car and each driver is the same as if one car at the same speed had collided head on with a concrete wall. d) Car 1 has mass \(m,\) and car 2 has mass \(2 m .\) In a head-on collision of these cars while moving at identical speeds in opposite directions, car 1 experiences a bigger acceleration than car 2 . e) Car 1 has mass \(m\), and car 2 has mass \(2 m\). In a headon collision of these cars while moving at identical speeds in opposite directions, car 1 receives an impulse of bigger magnitude than that received by car 2.
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