physics
posted by Katie .
A 500kg cannon and a supply of 80 cannon balls, each with a mass of 45.0 kg, are inside a sealed railroad car with a mass of 11000 kg and a length of 49 m. The cannon fires to the right; the car recoils to the left. The cannon balls remain in the car after hitting the wall. After all the cannon balls have been fired, what is the greatest distance the car can have moved from its original position?
What is the speed of the car after all the cannon balls have come to rest on the right side?

The center of mass of car and contents remains in the same place.
For greatest amount of displacement, assume that all the cannonballs move from one end to the other
The final speed is zero, since momentum is conserved 
I don't quite follow

The problem wants you to assume that the railroad car in on a frictionless track. Such cars do not exist, but assume this one rolls without friction, anyway. I hope you have heard of the law of conservation of momentum.
The initial momentum of the car and its contents is zero. The total momentum of the car and its contents must remain zero. When nothing moves inside the car, the car must also have zero velocity.
The first part of your question is harder to explain. In a problem such as this where you are not dealing with a rigid body, the momentum conservation equation still applies if for total momentum you use the total mass times the velocity of the center of mass.
In your problem, the center of mass does not move in Earthbased coordinates, because of the momentum conservation law. The train will move temporarily while the shooting is going on, and stop when it is over. The center of mass as seen from inside will move, but from outside it will not.
The motion of the center of mass as seen from inside equals the final displacement of the car.
Respond to this Question
Similar Questions

Physics
A cannon on a railroad car is facing in a direction parallel to the tracks. It fires a 99 kg shell at a speed of 105 m/s (relative to the ground) at an angle of 60.0° above the horizontal. If the cannon plus car have a mass of 5.5 … 
physics
A cannon on a railroad car is facing in a direction parallel to the tracks (the figure below ). It fires a 99kg shell at a speed of 105 m/s (relative to the ground) at an angle of 60 above the horizontal. If the cannon plus car have … 
Physics
A cannon of mass 200kg, fires a cannonball with a mass of 10kg. The cannon ball leaves the barrel of the cannon with a velocity of 60 m/s. Using the law of conservation of momentum , explain what happens to the cannon when the cannon … 
physics
A railway flat car is rushing along a level frictionless track at a speed of 45m/s. Mounted on the car and aimed forward is a cannon that fires 65 kg cannon balls with a muzzle speed of 625m/s. The total mass of the car, the cannon, … 
Physics
A 500 kg cannon rests on wheels that are free to roll. The cannon fires a 2 kg cannon ball horizontally with an average force of 400 N. What is the acceleration of the cannon ball? 
AP Physics
Momentum One of those Civil War cannons is fired. The Cannon has a mass of 873kg It fires a 35.0kg cannon ball at a velocity of 145 m/s at an elevation angle of 35.0 degrees. The length of the barrel is 2.10m. (a) What is the recoil … 
physics
A cannon is mounted on a railroad car. The cannon shoots a 1.75 kg ball with a muzzle velocity if 300 m/s. The cannon and the railroad car together have a mass of 4500 kg. if the ball, cannon, and railroad car are initially at rest, … 
physics
A spring cannon is fastened to a glider at rest on a horizontal frictionless air track. The combined mass of the cannon and the glider is 0.560kg. The cannon fires a ball with a mass of 50g horizontally at a speed of 14 m/s. How fast … 
physics
A 580 kg cannon and a supply of 41 cannon balls, each with a mass of 38.9 kg, are inside a sealed railroad car with a mass of 31000 kg and a length of 53 m. The cannon fires to the right; the car recoils to the left. The cannon balls … 
physics
A railway flat car is rushing along a level frictionless track at a speed of 45m/s. Mounted on the car and aimed forward is a cannon that fires 65 kg cannon balls with a muzzle speed of 625m/s. The total mass of the car, the cannon, …