# Read about conservation of momentum | 115 Discussions | Page 1

1. ### Velocity of a cart moving in the rain as a function of time

At time t = 0, the mass of the cart is ##M_0## and velocity is ##v_0## in a time interval ##dt## let a mass of ##dm## be added to the cart due to the pouring water and let the reduction in speed be ##dv## ##\lambda = dm/dt## applying conservation of momentum from the ground frame gives M_0...
2. ### I Conservation of angular momentum and its counterpart for linear momentum

Hi, I have just joined the forum. Thank you all for being a part of such places so that people like me can get answers to the questions on their minds! --------------------------- I have been trying to understand how a quadcopter yaws. Referring to the figure below which is bird's eye view of...
3. ### Cars Collide on a Hill, Conservation of Momentum Help Please

QUESTION: ----------- For the purposes of this problem, we will define the direction of Vehicle A's initial velocity as the positive direction: While driving on a road that is inclined at an angle of 10 degrees above the horizontal, Vehicle A and Vehicle B are in a head-on collision lasting...
4. ### Determining position of an object after inelastic collision

Homework Statement A 39,000 lb truck A and a 3968 lb sports car B collide at an intersection. At the moment of the collision, the truck and the sports car are traveling with speeds vA = 70 mph and vB = 30 mph. Assume that the entire intersection forms a horizontal surface. Letting the line of...
5. ### B Ballistocardiograph and conservation of momentum

Hi, once again I'm probably asking a question that is more about human physiology than physics (I recently asked a question that had to do with hearing). I found a (definitely too hasty) reference to a ballistocardiograph in a high school textbook. So I got curious about the way this apparatus...
6. ### Conservation of Momentum (Explosion Kinematics)

Homework Statement [/B] A 3200 kg space vehicle (including a launchable lifeboat) is travelling with a velocity of 300 m/s in a straight trajectory [East]. The lifeboat (200 kg) is fired at a speed of 1000 m/s [N of original trajectory]. a) After firing it is found that the horizontal...
7. ### Final velocities of two objects in a 2D elastic collision

Homework Statement An atomic nucleous of mass m travelling with speed v collides elastically with a target particle of mass 3.0m (initially at rest) and is scattered at 45o (a). What are the final speeds of the two particles? Advice: eliminate the target particle's recoil angle by...
8. ### Four men jumping from a raft

Suppose four men are on a square shaped raft.All have jumped mutually perpendicularly into the river from the raft at velocity 2m/s at the same time. What will be the velocity of the center of mass of the raft? The implied assumption is likely that the mass of the four men is same. I think the...
9. ### Simple Ice Skater with Conservation of Angular Momentum

Homework Statement Not a HW problem, but a "me re-thinking things" problem. Please tell me where my thinking is flawed: You have an ice skater with no net external torques acting on him/her. (We are analyzing the time after they have to get an external torque on them by pushing off of the...
10. ### Four friends jump from a raft

Homework Statement Suppose your three friends and you are on a square shaped raft. You all have jumped mutually perpendicularly into the river from the raft at velocity 2m/s at the same time. What will be the velocity of the center of mass of the raft? Homework Equations Maybe,the law of...
11. ### I Maximizing rocket velocity - shoot fuel at once, or slowly?

I stumbled upon a 3-year old article from Wired that poses this question on rockets: Suppose I have two rockets with a mass M and fuel mass m. Rocket A shoots all the fuel at once (again, like a nuclear propulsion engine) with a fuel speed of u and rocket B shoots two blobs of fuel—first a shot...
12. J

### D’Alambert vs Newton’s second law?

I’m a bit stuck with differentiating between the conservation of energy and D’Alambert. For a question I need to find the average resistance of the ground after it has been struck by an object. I chose to look at the equation as Ma + Mgh - Fr = 0. Can you advise if this is correct?
13. ### How do we know how long the force is acting on an object?

Hey all, so I'm self studying and I came across this question: A ## 2 kg ## cart, traveling on a horizontal air track with a speed of ## 3 m/s##, collides with a stationary ##4 kg## cart. The carts stick together. The impulse exerted by one cart on the other has a magnitude of: A. ## 0 ## B...
14. ### B Momentum transfer from linear to angular motion

I am trying to create a momentum trap to calculate the velocity of a projectile when it hits the trap. It essentially consists of a plate if known mass at the bottom of a pendulum of known radius. When the projectile hits the plate, the degrees that the pendulum rotates are recorded. I believe...
15. A

### Elastic Collision Angle Proof

Homework Statement Prove that in the elastic collision of two objects of identical mass, with one being a target initially at rest, the angle between their final velocity vectors is always 90 degrees. Homework Equations m1v1+m2v2 = m1v1'+m2v2' 1/2m1v1^2 +1/2m2v2^2 = 1/2m1v1'^2 + 1/2m2v2'^2...
16. A

### Elastic collision heavy particle problem

Homework Statement Suppose a heavy particle (mass m1) has an elastic head-on collision with a very light particle of mass m2 initially at rest. Show that if m1>>m2, the velocity of the projectile (m1) is practically unchanged, whereas the target particle (m2) acquires a velocity v2' = 2v1...
17. T

### Confusion with "explosive" part, Conservation of Momentum

Homework Statement A two-stage rocket is traveling at 4500 m/s before the stages separate. The 3000-kg first stage is pushed away from the second stage with an explosive charge, after which the first stage continues to travel in the same direction at a speed of 3000 m/s . How fast is the...
18. ### B Conservation of linear momentum in this system

A pet mouse sleeps near the eastern edge of a stationary, horizontal turntable that is supported by a frictionless, vertical axle through its center. The mouse wakes up and starts to walk north on the turntable. Is the momentum of the system constant? i understand that the initial momentum is...
19. B

### Conservation of Angular Momentum of Train on Disk

Homework Statement A horizontal plywood disk with mass 6.90 kg and diameter 1.14 m pivots on frictionless bearings about a vertical axis through its center. You attach a circular model-railroad track of negligible mass and average diameter 1.04 m to the disk. A 1.40 −kg , battery-driven model...
20. J

### Final speed and direction after a collision (elastic+inelastic)

Homework Statement A billiard ball moves at a speed of 4.00 m/s and collides ELASTICALLY with an identical stationary ball. As a result, the stationary ball flies away at a speed of 1.69 m/s. Determine a. the final speed and direction of the incoming ball after the collision b. the direction...
21. J

### Find speed and direction of a particle after collision

SOLVED THANK YOU
22. S

### Conservation of Work/Momentum of Puck Sliding Off Plate

Homework Statement I saw this problem from a few years ago here on Physics Forum (https://www.physicsforums.com/threads/work-energy-theorem-problem.823990/) and wanted some clarification. Here is the problem: A curved plate of mass M is placed on the horizontal, frictionless plane as shown...
23. ### B Kinetic theory of gases: rebound speed and force questions

Hi everyone, I remember years ago at school memorising the derivation of the formula for pressure in the kinetic theory of gases, as explained in this Youtube video: Thinking a little more deeply about this derivation there are two things I don't get: 1) At 0:53, the video says the molecule...
24. ### Need help with collision and conservation of momentum problem

Homework Statement Two blocks move along a horizontal frictionless surface and collide head-on with each other. The mass of the first block, moving to the right with speed v is m, and the mass of the second block moving towards the left with speed 3v is 2m. After the collision, the block of...
25. ### Elastic collision -- Energy & Momentum

Homework Statement Please see the attached photo. (down) Hminitial= 1.5R M = 2/3m Perfectly elastic collision What is the velocity of object m immidiatly after the collision? (by m,g,R) Homework Equations Conservation of energy Conservation of momentum The Attempt at a Solution I assumed...
26. ### Splitting/Exploding object & Momentum

Hi, Homework Statement A free falling object of mass "m" falling from some height, collides the floor in speed of 20 m/s (perfectly elastic collision). In his 1/2 height back up he splits into 2 pieces- ¼m which going downward and ¾m keeping upward. The ¼m reaching the floor after ½ second. 1)...
27. ### Rotating rod

Homework Statement A uniform rigid scale is held horizontally with one of its end at the edge of the table and the other supported by hand. Some coins of negligible mass are kept on the meter scale. As the hand supporting the scale is removed, the scale starts rotating about its edge on the...
28. ### Conservation of Angular Momentum with SHM

Homework Statement A 39.00 kg rod of length 2.8 m is hanging vertically by one of its ends that is free to swing in a complete circle about a frictionless axle/pivot. The rod has uniform mass density. Suddenly it is struck horizontally by a 5 kg putty that sticks to the center of...
29. ### Trying to solve conservation of momentum problem

Homework Statement its a nuclear physics problem : a deuterium atom with energy 4Mev collides with a boron atom B5/10 in an elastic collision producing an H1/1 and B5/11 ,the Q of the reaction = 9.23 Mev . find the E,E' , the energy of the boron and the hydrogen the unknowns : E,E', theta of...
30. ### How is momentum conserved in a Gauss Gun?

Homework Statement So for those who aren't familiar with the Gauss Gun here is a video demonstrating its function: As you can see in the video, a steel ball is rolled towards a sequence of magnets and other steel balls and as the incoming ball strikes the magnet, the ball on the other end...