# physics

posted by .

i need some help wih this, thanks!!

Blocks A and B are moving toward each other along the x axis. A has a mass of 2.0 kg and a velocity of 50 m/s ( in the positive x direction ), while B has a mass of 4.0 kg and a velocity of -25 m/s ( in the negative x direction). They suffer an elastic collision and move off along the x axis. After the collision the velocities of A and B, respectively are:
a -50 and 25 m/s
b 50 and -25 m/s
c -25 and 50m/s
d 25 and -50 m/s
e -25 and -50 m/s

Momentum is conserved:
2*50+4*(-25)=0 so the final momentum has to be zero. Which also means they are going in opposite directions, which means that A has a neg v eloctiy, and B a positive velocity. Answers A, c fit that. Now, a is zero momentum. And c is zero momentum.

Conservation of energy:

Initial energy: 1/2 2*50^2 + 1/2 4*25^2 equals something. You can see that answer a is the only answer possible.

thankyou

## Similar Questions

1. ### physics

A 1.6 kg particle moving along the x-axis experiences the force shown in the figure. The particle's velocity is 4.2 m/s at x = 0 m. The figure or graph has F (N) along the y axis and velocity along the x axis. A diagonal line drops …
2. ### physics

A 1.6 kg particle moving along the x-axis experiences the force shown in the figure. The particle's velocity is 4.2 m/s at x = 0 m. The figure or graph has F (N) along the y axis and velocity along the x axis. A diagonal line drops …
3. ### physics

Two masses are involved in an elastic collision. The first has a mass of 0.150 kg and an initial velocity of 0.900 m/s directed at an angle of 50 degrees with the positive y-axis as shown below. The second mass, of 0.260 kg moves along …
4. ### PHYSICS

Blocks A (mass 2.50 kg) and B (mass 10.00 kg) move on a frictionless, horizontal surface. Initially, block B is at rest and block A is moving toward it at 5.00 m/s. The blocks are equipped with ideal spring bumpers. The collision is …
5. ### physics

Two billiard balls of equal mass move at right angles and meet at the origin of an xy coordinate system. Ball A is moving upward along the y axis at v_A = 2.0m/s , and ball B is moving to the right along the x axis with speed v_B = …
6. ### Physics

A ball with a mass of 0.50 kilograms is moving at a speed of 1.8 meters/second along the positive x-axis. It collides with another ball of the same mass travelling at a speed of 2.0 meters/second toward the positive y-axis. Both balls …
7. ### Physics

Question 2. 3 Consider a box that explodes into two pieces while moving with Fig. 9-24 a constant positive velocity along an x axis. If one piece, with mass : m1, ends up with positive velocity v1, then the second piece, with : mass …
8. ### physics

Blocks A A (mass 6.50kg kg ) and B B (mass 10.50kg kg ) move on a frictionless, horizontal surface. Initially, block B B is at rest and block A A is moving toward it at 4.00m/s m/s . The blocks are equipped with ideal spring bumpers. …
9. ### PHYSICS

Chapter 07, Problem 48 Two particles are moving along the x axis. Particle 1 has a mass m1 and a velocity v1 = +5.0 m/s. Particle 2 has a mass m2 and a velocity v2 = -7.9 m/s. The velocity of the center of mass of these two particles …
10. ### physics

Two balls have the same mass. One ball moving along the positive x-axis and the other ball moving along the positive y-axis undergo perfectly inelastic collision. What can you say about the motion of the balls after the collision?

More Similar Questions