Collision Conservation of Energy

AI Thread Summary
The discussion centers on a collision problem involving two railroad cars, where one car collides with a stationary car of equal mass. The initial kinetic energy of the moving car is calculated, but confusion arises regarding the type of collision and the conservation principles involved. Participants clarify that this scenario represents an inelastic collision since the cars lock together after the impact, meaning momentum is conserved while kinetic energy is not. The importance of understanding the distinction between elastic and inelastic collisions is emphasized, along with the need to apply conservation of momentum rather than energy for this type of collision. Overall, the focus is on correcting misconceptions about collision types and the principles that govern them.
jakeginobi

Homework Statement


a 5.0 x 10^5kg railroad car moving at 8.0m/s. collides with a stationary railroad car of equal mass. after the collision the two cars lock together and slide forward. What is the final velocity of the wrecked cars?
using conservation of energy
M1 = 5.0 x 10^5 kg
M2 = 5.0 x 10^5
Vi1 = 8.0m/s
Vi2 = 0m/s
Vf = ?

Homework Equations


Ek = 1/2mv^2

The Attempt at a Solution


I didn't know where to start, I found the kinetic energy of the railroad car(1.6 x10^7 J) and added it to the stationary one - since it's stationary the railroad car would initially have 0 kinetic energy
 
  • Like
Likes mechpeac
Physics news on Phys.org
My teacher didn't teach us how to solve collision questions using conservation of energy
 
What type of collision does this scenario represent? What's conserved and what's not conserved in such a collision?
 
  • Like
Likes mechpeac
I believe it represents an elastic collision, and conservation of energy/momentenum is conserved. They both lock on together after collision and move as one.
 
jakeginobi said:
I believe it represents an elastic collision, and conservation of energy/momentenum is conserved. They both lock on together after collision and move as one.
Review the properties of the collision types. You've got things backwards.
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Momentum and kinetic energy of collision between two identical railroad cars
Replies
1
Views
13K
Finding two objects velocity after an elastic collision
Replies
10
Views
4K
Potential and Kinetic energy equations including drag coefficient
Replies
1
Views
1K
Confused about a conservation of energy problem
Replies
4
Views
2K
Momentum in a perfectly inelastic collision
Replies
6
Views
2K
Conservation of momentum (wrecking ball hits a stationary object)
Replies
10
Views
3K
Conservation of Energy with changing masses on ice
Replies
2
Views
1K
Ambiguous question on momentum and how it works...
Replies
13
Views
1K
Finding kinetic energy consevered after collision
Replies
4
Views
2K
Potential Energy - 2D inelastic collision - ballistic pendulum
Replies
10
Views
2K

Hot Threads

Recent Insights

Back
Top