# Crumple zones in cars, safety equipment and thin sponges

#### xo-hikari

Hello! I have a few questions that would be awesome if someone could answer....

1. An egg dropped from 1m, for example, will break if it lands on concrete, but not if it lands on a thin sponge, even thought they experience the same impulse from each drop. WHY?

2. I have heard that cars today are designed with "crumple zones". How does this protect the occupants of the car?

3. For example, in football, safety equipment is very important in protecting the player. How do what they wear minimize their risk of injury and how has it affected the sport?

Thanks so much for helping!

#### werehk

PHF Hall of Fame
Hello! I have a few questions that would be awesome if someone could answer....

1. An egg dropped from 1m, for example, will break if it lands on concrete, but not if it lands on a thin sponge, even thought they experience the same impulse from each drop. WHY?

2. I have heard that cars today are designed with "crumple zones". How does this protect the occupants of the car?

3. For example, in football, safety equipment is very important in protecting the player. How do what they wear minimize their risk of injury and how has it affected the sport?

Thanks so much for helping!
For question 1, even though the impulse is the same. However, the rate of change of momentum(impulse) is not the same. For hard object, the impact time is very much smaller compared to soft surfaces, so the average force of impact acting on egg would smaller for soft land.

For question 2,3, the reasons are similar

#### lyming117

F=(mv2-mv1)/t , this is implusive force
Ft , this is impulse ...
the egg didnt break when on soft surface is because the time of impact is lengthen, thus resulting the impulsive force to be smaller as t is greater ...(math)
3. safety equip (well it depends what type is it) but i suppose is the same subject we are talking about ... therefore safety equip helps to enlengthen the time of impact ... and also it serves as to protect us from frictional force as we fall on the ground ...

#### the curious

Hello! I have a few questions that would be awesome if someone could answer....

1. An egg dropped from 1m, for example, will break if it lands on concrete, but not if it lands on a thin sponge, even thought they experience the same impulse from each drop. WHY?

2. I have heard that cars today are designed with "crumple zones". How does this protect the occupants of the car?

3. For example, in football, safety equipment is very important in protecting the player. How do what they wear minimize their risk of injury and how has it affected the sport?

Thanks so much for helping!
The answer for 2 is that crumple zones on collision crumple and absorb the energy produced by the collision saving the occupants from harm.

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