You would use Newton's Second Law of Motion to find the acceleration of the boulder. Here's the formula:

F = m * a

Where:

* F is the force applied (in Newtons, N)

* m is the mass of the object (in kilograms, kg)

* a is the acceleration of the object (in meters per second squared, m/s²)

To solve for acceleration (a), rearrange the formula:

a = F / m

Now plug in the values:

* F = 65 N

* m = 10 kg

a = 65 N / 10 kg = 6.5 m/s²

Therefore, the acceleration of the boulder is 6.5 m/s².