Some basic questions about collision force

In summary, the conversation discusses the concept of force and momentum in collisions, specifically in the context of Newton's 3rd law and inelastic collisions. The follow-up questions inquire about determining the force upon impact and the energy produced in a collision. The response suggests using the conservation of momentum and determining the change in momentum over the collision time to calculate the average force. It also mentions that inelastic collisions do not conserve kinetic energy and the information provided in question 2 may be insufficient. Additionally, it mentions that modern cars have features to absorb shock in collisions.
  • #1
12thString
5
0
1. a small car and a big truck collided. as Newton's 3rd law states, they should apply the same amount of force with each other. so if the big truck has a mass of (just to make it simple) 5kg and acc of 2m/s to the right and the small car has a mass of 2kg and acc of 3m/s to the left. (Ftruck=+10N, Fcar=-6N) of course the car has a smaller force, but as stated above, upon collision, they should have the same force? how do i determine that force given their initial[?] forces. please clarify me on this. a follow up question would be that if given the initial forces acting on two known masses, how can i determine the force upon their impact?

2. I've read in a magazine that when 2 motorbikes collide, they'll produce roughly 124K N of energy. Given that their initial velocity is the same at 50mph (22.2m/s, one positive and one negative of course since this is just one dimensional collision) and their masses are 80 and 90kg with a collision time of 0.015s, i was wondrin with how they derived this 124K N of force. I can't use conservation of momentum (and F=m[tex]\Delta[/tex]v/[tex]\Delta[/tex]t also) since i can't assume that they have zero final velocity as that would mean that they have the same mass. how should i use the given variables?


please enlighten me guys. ^^
 
Last edited:
Physics news on Phys.org
  • #2
In inelastic collisions, the total momentum is conserved, so the momentum before is equal to the momentum after. Then determine the change in momentum of each mass and divide by the time over which it occurs. That would given an averate force over that time period (collsion time).

http://hyperphysics.phy-astr.gsu.edu/hbase/inecol.html

In inelastic collisions, the kinetic energy is not conserved.
 
  • #3
does that mean that the information provided in question number 2 is insufficient?

and how about question number 1?

thanks for the reply.
 
Last edited:
  • #4
The cars made now are ones that absorb the shock for an instant, giving you time to react or buckle you feet and prepare for impact.
 

1. What is collision force?

Collision force is the force that is exerted when two objects collide with each other. It is equal to the change in momentum of the objects involved in the collision.

2. How is collision force calculated?

Collision force can be calculated using the formula F = m * Δv, where F is the collision force, m is the mass of the object and Δv is the change in velocity of the object after the collision.

3. What factors affect collision force?

The factors that affect collision force include the mass and velocity of the objects involved in the collision, as well as the duration of the collision and the direction of the forces.

4. Can collision force be negative?

Yes, collision force can be negative if the objects involved in the collision are moving in opposite directions. This means that the objects are exerting a force on each other in the opposite direction of their motion.

5. How does collision force relate to everyday life?

Collision force is relevant in many aspects of everyday life, such as car accidents, sports collisions, and even simple activities like bouncing a ball. Understanding collision force can help us better understand and predict the outcomes of these events.

Similar threads

Replies
6
Views
1K
Replies
28
Views
1K
Replies
3
Views
923
  • Introductory Physics Homework Help
Replies
6
Views
717
  • Mechanics
Replies
4
Views
1K
Replies
32
Views
4K
  • Mechanics
Replies
2
Views
926
  • Introductory Physics Homework Help
Replies
2
Views
1K
Back
Top