Understand Momentum & Energy Conservation in Ballistic Pendulum Problems

AI Thread Summary
In a ballistic pendulum problem, momentum is conserved during the collision between the bullet and the block because there are no external forces acting on the system. However, energy is not conserved during this collision due to the presence of friction, which dissipates energy. After the bullet lodges into the block, the system moves upward, and energy conservation applies as gravitational potential energy is converted from kinetic energy. The confusion arises from the distinction between the collision phase and the subsequent motion of the block. Understanding these principles clarifies the conservation laws in different stages of the ballistic pendulum problem.
IKonquer
Messages
47
Reaction score
0
In solving a ballistic pendulum problem, you can break it up into two parts:

(1) A bullet is fired and it lodges into a block.
Momentum is conserved because there is no net external force.
Energy is not conserved because there is friction between the block and bullet.

(2) Once the bullet is lodged into the block, the block moves up a certain vertical distance.

Could someone explain:

Why is momentum not conserved in this case?

Why is energy conserved in this case?
 
Last edited:
Physics news on Phys.org
Don't you have the parts in bold the wrong way around?
 
Thread 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
View full post »
Thread 'A cylinder connected to a hanged mass'

Thread 'A cylinder connected to a hanged mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Kinetic energy and momentum in circular paths
Replies
4
Views
2K
Angular momentum for a bullet and a rod attached to a ceiling
Replies
17
Views
1K
Is Linear Momentum Conserved in This Case? (sliding box hits a floor tile)
Replies
2
Views
846
Momentum conservation (ballistic pendulum)
Replies
2
Views
1K
Linear momentum problem (ballistic pendulum)
Replies
2
Views
4K
Conservation of Energy Problem -- bullet fired into a ballistic pendulum
Replies
7
Views
6K
Conservation of Momentum Problem - Mechanical and Kinetic Energies
Replies
2
Views
891
Potential Energy - 2D inelastic collision - ballistic pendulum
Replies
10
Views
2K
Physics problem - Momentum and energy
Replies
25
Views
2K
Ballistic Pendulum initial velocity of bullet
Replies
2
Views
3K

Hot Threads

Recent Insights

Back
Top