Is there a difference between contact time and impact time? (collsion)

In summary, the conversation is discussing the concepts of impact time and contact time in relation to collisions. Impact time refers to the brief moment when a velocity changes to zero upon impact, while contact time is the longer period of time in which an object remains in contact with another object. This is illustrated by the example of jumping and hitting the ground. The conversation also addresses the scenario of two vehicles colliding and bouncing off each other, and concludes that the contact time would be the same as the collision time in this situation.
  • #1
question dude
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0
This is from my textbook:

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I'm slightly confused about the bit underlined in red. Do you think its in reference to the sentence just before where it talks about situations of vehicles remaining tangled? (so for other cases, contact time = impact time, right?)

also, I don't really understand how to picture the scenario of the two vehicles remaining tangled together and 'how they exert forces on each other until they move at the same velocity'.
 
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  • #2


You drop from 2 floors up and smash into the ground. SPLAT! Your impact time is the very short time when your velocity changes from some value v (just about to hit the ground) to zero (i.e. you are now at the same velocity as the ground). Your contact time is very long and stops until someone scrape you off the ground, i.e. the time you are in contact with the floor.

Zz.
 
  • #3


ZapperZ said:
You drop from 2 floors up and smash into the ground. SPLAT! Your impact time is the very short time when your velocity changes from some value v (just about to hit the ground) to zero (i.e. you are now at the same velocity as the ground). Your contact time is very long and stops until someone scrape you off the ground, i.e. the time you are in contact with the floor.

Zz.

I see now. So what if you have two cars colliding head on and bouncing off each other? would contact time be the same as collision time in this situation?
 
  • #4


question dude said:
I see now. So what if you have two cars colliding head on and bouncing off each other? would contact time be the same as collision time in this situation?

Correct.

Zz.
 
  • #5


ZapperZ said:
Correct.

Zz.

many thanks!
 

1. What is the difference between contact time and impact time?

Contact time refers to the duration of time that two objects are in direct contact with each other during a collision. Impact time, on the other hand, refers to the duration of time that it takes for an object to come to a complete stop after a collision. So, while contact time is the time during which the objects are actually in contact, impact time includes the time it takes for the objects to separate after the collision.

2. How do contact time and impact time affect the outcome of a collision?

The longer the contact time, the more time there is for the objects to exert a force on each other, resulting in a larger impact force. On the other hand, a shorter contact time results in a smaller impact force. Similarly, a longer impact time means that the objects are slowing down at a slower rate, resulting in a smaller impact force, while a shorter impact time means that the objects are slowing down at a faster rate, resulting in a larger impact force.

3. Is there a way to calculate contact time and impact time?

Yes, contact time and impact time can be calculated using the formulas: contact time = impulse/mass, and impact time = velocity/change in velocity. Impulse is the product of force and contact time, and change in velocity is the difference between the initial and final velocities of the objects involved in the collision.

4. How do factors like mass and velocity affect contact time and impact time?

Mass and velocity both play a role in determining the contact time and impact time of a collision. Objects with larger masses will typically have longer contact times and shorter impact times, resulting in a larger impact force. Similarly, objects with higher velocities will have shorter contact times and longer impact times, resulting in a larger impact force.

5. Can contact time and impact time be manipulated in a collision?

Yes, the contact time and impact time of a collision can be manipulated by changing the initial velocities and masses of the objects involved. For example, if the initial velocities are increased, the contact time will decrease and the impact time will increase, resulting in a larger impact force. Additionally, the materials and surfaces of the objects can also affect the contact time and impact time, as objects with more elastic materials will have longer contact times and shorter impact times compared to objects with less elastic materials.

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