Gravitational force on an anvil.

The force on an object determines its acceleration. If the force is constant within a region of space, the acceleration on the object will be constant. Let us discuss the two most important constant force environments for MCAT problem solving: the uniform gravitational field and the uniform electric field.

In this Discussion, we are starting a thread which will be winding through the Discussions for the next several modules, the comparison and contrast of gravitational and electric force. In the context of Kinematics, this is particularly relevant when discussion the motion involving constant acceleration, because constant acceleration problem solving often involves the free-fall or projectile motion of an object within a uniform gravitational field or the similar motion of a charged particle in the space between electrified plates.

Both gravitational fields and electric fields can be very nearly constant across a region of space, leading to constant acceleration in that region.

Constant acceleration environments appear often on the MCAT, whether gravitational or electrostatic. What are the constant acceleration environments for gravitational and electrostatic force?

The commonly seen gravitational model system involving constant acceleration involves an object moving near the earth's surface. The electrical model system of constant acceleration includes a particle moving between charged plates.

In other words, the region of space between a parallel plate capacitor produces simple kinematics upon a charged particle much like the constant gravitational force acting near the Earth's surface leads to simple Kinematics for a projectile. Both situations involve Dynamics of constant force and thus, the Kinematics of constant acceleration.

The fact that the motion of a charged particle between capacitor plates has both similarities and differences to projectile motion makes it a good subject for MCAT questions. In fact, you are much more likely on the MCAT to be put in the position of applying the conceptual reasoning you learned in projectile motion to the motion of a charged particle between capacitor plates than to face a straightforward projectile motion problem.