Return to Blog Homepage

MCAT Physics Question — Object Acceleration

An object rests on a plane, with an angle of incline, θ, an acceleration due to gravity, g, and a coefficient of friction μ between the object and the plane. Which of the following gives the acceleration of the object?


A. a = g sin θ

B. a = g (sin θ – cos θ)

C. a = g (cos θ – μ sin θ)

D. a = g (sin θ – μ cos θ)

Click for Explanation

The force of gravity down the plane is given by Fg = mg sin θ. The frictional force is given by Ff = μ mg cos θ.

Thus, we can set up the overall equation:

Fnet = Fg – Ff

Applying Newton’s Second Law, we can re-write the equation as:

ma = Fg – Ff

Substituting the equations given for Ff and Fg we get:

ma =  mg sin θ –  μ mg cos θ

Canceling out “m” throughout the equation and factoring out the “g” leaves us with:

a = g (sin θ – μ cos θ)

Thus, choice (D) is the right answer.

Want more MCAT practice?

We’ve got options for every schedule and learning style!

From the best online MCAT course created by top instructors with 524+ MCAT scores to the most representative full-length practice exams and private tutoring, we can custom tailor your MCAT prep to your goals!

Not sure which option is right for you? Schedule a free MCAT consultation with an MCAT expert using the form below. No obligation, just expert advice.

Create your Free Account to access our MCAT Flashcards SIGN UP NOW