In AP Physics 1, vertical motion is motion along the up-down axis where gravity produces a constant downward acceleration of about 9.8 m/s², so the kinematics equations for constant acceleration apply, whether the object is dropped, thrown up, or part of a projectile's path.
Vertical motion is any motion along the up-down direction near Earth's surface. What makes it special on the AP exam is that the acceleration is constant and known. Gravity pulls every object downward at roughly 9.8 m/s² (often rounded to 10 m/s² on the exam), regardless of the object's mass. That means all four constant-acceleration kinematics equations work, and you already know one of the variables before the problem even starts.
The part that trips people up is the velocity-acceleration relationship. Throw a ball straight up and its velocity decreases, hits zero at the peak, then increases downward. But the acceleration never changes. It stays 9.8 m/s² downward the entire flight, including at the very top. Velocity can be zero while acceleration is not. If air resistance is negligible, this vertical motion is called free fall, and the time up equals the time down for a ball returning to its launch height.
Vertical motion lives in Unit 1 (Kinematics) of AP Physics 1, where you describe motion using position, velocity, and acceleration. It's also the backbone of projectile motion, because every projectile problem splits into two independent pieces. The horizontal piece has constant velocity, and the vertical piece is just vertical motion with acceleration g. If you can solve a ball-thrown-straight-up problem, you can solve the vertical half of any projectile problem with the exact same equations.
It also feeds forward into Unit 2 (Dynamics). The reason vertical acceleration is constant is that the only force acting in free fall is gravity, and gravitational force is proportional to mass. So Newton's second law gives every object the same acceleration g. That mass-cancels insight shows up repeatedly in MCQs.
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Free fall (Unit 1)
Free fall is vertical motion in its purest form, when gravity is the only force acting. A dropped ball, a ball thrown straight up, and a ball thrown straight down are all in free fall the moment they leave your hand.
Acceleration due to gravity (Unit 1)
The number that makes vertical motion solvable. Near Earth's surface, g is about 9.8 m/s² downward and it does not depend on mass, which is why a bowling ball and a marble dropped together hit the ground at the same time (ignoring air resistance).
Projectile motion (Unit 1)
A projectile is just vertical motion and horizontal motion happening at the same time, independently. The vertical component accelerates at g while the horizontal component coasts at constant velocity. Solve them separately and time is the variable that links them.
Forces and Newton's second law (Unit 2)
Vertical motion explains why g is the same for everything. Gravitational force equals mg, so when you divide by mass in F = ma, the mass cancels and every object accelerates at g.
Vertical motion shows up constantly even when the question never says the phrase. Classic MCQ stems include a ball thrown straight up (what are velocity and acceleration at the peak?), objects of different masses dropped together, and ranking the speed of a ball at the same height going up versus coming down. The acceleration-at-the-peak question is a famous trap, since the answer is 9.8 m/s² downward, not zero. On FRQs, vertical motion is usually the engine inside a projectile or kinematics problem. You'll need to choose a positive direction, keep your signs consistent for velocity and acceleration, and use a kinematics equation to solve for time, height, or final velocity. Graph questions are common too, so be ready to recognize that vertical free-fall motion gives a straight-line velocity-time graph with slope -g and a parabolic position-time graph.
Vertical motion is the broader category, any up-down movement at all, including an elevator rising at constant speed or a parachutist with air resistance. Free fall is the special case where gravity is the only force, so the acceleration is exactly g. All free fall is vertical motion (or has a vertical component), but not all vertical motion is free fall. On the exam, 'free fall' is your signal to set a = 9.8 m/s² downward and ignore everything else.
Vertical motion near Earth's surface has a constant acceleration of about 9.8 m/s² directed downward, so the constant-acceleration kinematics equations apply.
At the top of a thrown object's path, the velocity is zero but the acceleration is still 9.8 m/s² downward; this is one of the most common trap answers on the exam.
Acceleration due to gravity does not depend on mass, so a heavy and a light object dropped together hit the ground at the same time when air resistance is negligible.
In projectile motion, the vertical component behaves exactly like an object thrown straight up or dropped, completely independent of the horizontal motion.
For an object launched up and returning to the same height, the time up equals the time down, and the speed at any given height is the same going up as coming down.
Pick a positive direction at the start of every vertical motion problem and keep velocity and acceleration signs consistent with it.
Vertical motion is movement along the up-down axis, where gravity produces a constant downward acceleration of about 9.8 m/s². Because the acceleration is constant, you can solve these problems with the standard kinematics equations from Unit 1.
No. The velocity is zero for an instant at the peak, but the acceleration is still 9.8 m/s² downward the whole time. If acceleration were zero at the top, the ball would just hover there.
Free fall is vertical motion where gravity is the only force, giving an acceleration of exactly g. Vertical motion is the broader idea and can include other forces, like air resistance on a parachutist or the normal force in a moving elevator.
No, not when air resistance is negligible. Gravitational force is proportional to mass, so the mass cancels in Newton's second law and every object accelerates at the same 9.8 m/s². This is a favorite AP misconception question.
A projectile's motion splits into independent horizontal and vertical parts. The vertical part is ordinary vertical motion with acceleration g, the horizontal part moves at constant velocity, and the time of flight links the two.
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