Conceptual Physical Science Explorations
Conceptual Physical Science Explorations
2nd Edition
ISBN: 9780321567918
Author: Paul G. Hewitt, Leslie A. Hewitt, John A Suchocki
Publisher: Addison Wesley
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Textbook Question
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Chapter 5, Problem 6RQ

If you’re in a car with faulty brakes and you have to hit something to stop, the momentum will change to zero whether you hit a brick wall or a haystack. So why is hitting a haystack a safer bet?

Expert Solution & Answer
Check Mark
To determine

The reason behind hitting a haystack is a safer bet as compared to a brick wall.

Answer to Problem 6RQ

The reason behind hitting a haystack is a safer bet as compared to a brick wall because haystack will exert small force resulting in less damage.

Explanation of Solution

The impulse is the quantity imparted to a body, which is equal to the multiplication of force applied on the object and the time for which the force is acting. This can be expressed as,

I=Ft

Here,

F is the force

t is the time

The quantity impulse of an object is equal to the change in momentum, which can be represented as,

I=ΔpI=p2p1

p2 is the final momentum

p1 is the initial momentum

So, it can be written as,

p2p1=Ft

When the object comes to rest, the final momentum becomes zero. Thus, the expression can be written as,

Ft=0p1F=p1t

The negative force value indicates that a retarding force is acting on the body. The quantity force is inversely proportional over the time in which a person is brought to rest, which can be seen from the above expression. Thus, a small-time will result in large force. In the case, when a car hits a brick wall, the car comes to rest in a very small amount of time. As a result, a larger force will be exerted on the car, causing more damage and injury to the car and occupant. On the other hand, when the car hits the haystack, the time taken by the car to come to rest becomes more. Hence, a smaller force is experienced by the car, resulting in less damage and injuries.

Conclusion:

Therefore, the reason behind hitting a haystack is a safer bet as compared to a brick wall because haystack will exert small force resulting in less damage.

Chapter 5 Solutions

Conceptual Physical Science Explorations

Ch. 5 - Which is the greater change in momentum, stopping...Ch. 5 - Which requires the greater impulse, stopping...Ch. 5 - When can the momentum of two moving objects be...Ch. 5 - What does it mean to say that momentum (or any...Ch. 5 - When a cannonball is fired, its momentum does...Ch. 5 - When a cannonball is fired, the cannon recoils. Is...Ch. 5 - When a cannonball is fired, is momentum conserved...Ch. 5 - Distinguish between an elastic collision and an...Ch. 5 - Railroad car A rolls at a certain speed and makes...Ch. 5 - If the equally massive cars of the previous...Ch. 5 - Calculate the momentum of a 10kg bowling ball...Ch. 5 - Calculate the momentum of a 50-kg carton that...Ch. 5 - Calculate the impulse that occurs when an average...Ch. 5 - Calculate the impulse that occurs when the same...Ch. 5 - The balls have different masses and speeds. (a)...Ch. 5 - Evan pushes crate starting at rest across a floor...Ch. 5 - When rollerblading, why is a fall less harmful on...Ch. 5 - In terms of impulse and momentum, why do air bags...Ch. 5 - Prob. 3TECh. 5 - In terms of impulse and momentum, why are nylon...Ch. 5 - If you throw an egg against a wall, the egg will...Ch. 5 - A lunar vehicle is tested on Earth at a speed of...Ch. 5 - Which has the greater momentum when they move at...Ch. 5 - In answering the preceding exercise, perhaps you...Ch. 5 - Why do 6-ounce boxing gloves hit harder than...Ch. 5 - Which undergoes the greatest change in momentum:...Ch. 5 - In the preceding question, in which case is the...Ch. 5 - If a fully loaded shopping cart and an empty one...Ch. 5 - A fully dressed person is at rest in the middle of...Ch. 5 - Michael throws a ball horizontally while standing...Ch. 5 - Two football players have a head-on collision and...Ch. 5 - In the previous chapter, rocket propulsion was...Ch. 5 - When you are travelling in a car at highway speed,...Ch. 5 - If an 18-wheeler tractor-trailer and a sports car...Ch. 5 - Your friend says that law of momentum conservation...Ch. 5 - How much impulse is needed to stop a 10kg bowling...Ch. 5 - A car with a mass of 1000kg moves at 20m/s. Show...Ch. 5 - A car carrying a 75kg test dummy crashes into a...Ch. 5 - Jane (mass 40.0kg), standing on the slippery ice,...Ch. 5 - A 2kg ball of putty moving to the right has a...Ch. 5 - A railroad diesel engine weighs four times as much...Ch. 5 - Prob. 7TSCh. 5 - A 1kg ostrich egg is thrown at 2m/s at a bedsheet...Ch. 5 - If fast Freddy doubles his running speed, what...Ch. 5 - A 1kg ball has the same speed as a 10kg ball....Ch. 5 - Two iron, balls, one twice the mass of other, are...Ch. 5 - If the mass of a cart full of groceries decreases...Ch. 5 - Your friend says that the impulse equals momentum....Ch. 5 - The impulse-momentum relationship is a direct...Ch. 5 - Which of the following equations best illustrates...Ch. 5 - When you jump from an elevated position to the...Ch. 5 - Standing on a stakeboard, you toss a ball...Ch. 5 - A big fish swims upon and swallows a small fish at...
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