A particle is projected from the bottom of an inclined plane of an inclination 30° with the velocity of 40m/s at the angle 60° with the horizontal. Find the speed of the particle when its velocity is parallel to the plane .take g=10m/s*2.

1. Draw the figure of the situation so that you can see better what the exact situation is.

2. Now we are going to take vector components along the slope of the inclined plane but not along the usual directions, this means that you have to consider velocity as u(cos30)i+ u(sin 30)j. Also take components of gravity(g) along the plane which is g(cos60)(-i) + g (sin 60)(-j).

3. Now you can find the velocity of the particle at any given time.The problem is like identical to a 2-d situation hence equate the velocity in the j direction to 0 and put the value in the other equation.