Question

This time we have a crate of mass 21.0 kg on an inclined surface, with a coefficient of kinetic friction 0.179. Instead of pushing on the crate, you let it slide down due to gravity. What must the angle of the incline be, in order for the crate to slide with an acceleration of 7.14 m/s^2?

a. 42.0 degrees

b. 55.9 degrees

c. 28.0 degrees

d. 72.7 degrees

Answer 1

The crate's acceleration can be calculated by first calculating the net force on it.

To simplify this, we rearrange the equation and square it

We know have a quadratic equation in term of cosine square. We use the substitution to simplify it.

We discard the negative value, as we know the slope is between zero and ninety degrees for which cosine returns a positive value.

Hence, Option B is correct.