How do you do this physics problem?
A cannon on a railroad car is facing in a direction parallel to the tracks (the figure below). It fires a 97 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 5.5 104 kg, what is the recoil speed of the car if it was at rest before the cannon was fired?
Comments
you need to do this in terms of momentum vector components. you have a 60 degree angle so you can resolve that into horizontal and vertical component. work out what your horizontal component is via trigonometry of the triangle you form from splitting your overall momentum vector into perpendicular components.
then, you can use momentum conservation to say what ever horizontal component the cannon ball has, the car has in the opposite direction. therefore you can work out its horizontal speed since you know its mass.