To find the angle between and , we first need to understand the relationship between force and momentum. The force acting on a particle is related to the rate of change of its linear momentum with respect to time, as described by Newton's second law of motion:

Given the expression for the momentum , we can find by differentiating with respect to :

So, .
Now, to find the angle between and , we use the dot product formula:

where is the angle between and . However, in this case, it's more insightful to see if and are orthogonal (at a angle to each other), because the dot product of two perpendicular vectors is zero.

The dot product of and is:

The result is zero, indicating that the angle between and is indeed .