How do I solve projectile motion problems in physics?

Answer 1

Projectile problems are used in classical mechanics to introduce 2 dimensional kinematics after first learning 1 dimensional kinematics, preparing for working with physics in several dimensions. The simplification of constant acceleration allows you to focus only on the multidimensional aspects without having to to worry (yet) about changing dynamics. However, projectile problems can be asked in many different ways and you don't want to be surprised on a test with a problem that upset your problem solving, perhaps taking too much time or leading you to make simple calculation errors. I can work with you so you understand where these problems are coming from and how to choose the best strategies to solve whatever problems get thrown at you quickly and accurately. In the attached video I run through very quickly what you need to know and show a couple of examples of the kinds of problems you might see. They are problems I give my undergraduate students in classical mechanics. The key things you need to understand (the first slide I show in the video) are these:

1. The basic idea: for relatively short (≲ 20 km) flight paths, the acceleration of gravity is nearly constant, pointed down, and generally air resistance is neglected.
2. With those assumptions the kinematics with constant acceleration in 1 dimension can easily be generalized to two independent dimensions, but with the time of flight linking them.
3. There is a small set of equations that are useful solving problems but which ones you choose to use can make the solution easier or harder, so matching the equations you use to the problem statement is important.
4. There are simple methods to use to select the best way to solve projectile problems

The little video might help you as it is. You should be able to stop it at different times and look over things in detail. It would take me about an hour or so to walk through them with you carefully so you understand everything and can do problems like those discussed. After that you can work a few practice problems and we can talk again to go through each one, making sure you get the strategy and will be able to solve any test question they throw at you. This is my first time using the Wyzant tools and my first video recording on them (I use Zoom in my university classes) and I hope it turns out OK for you.

Answer 2

Projectile motion combines horizontal and vertical motions. The trick is to break the motion into two components:

1. Horizontal: constant velocity (no acceleration)
2. Vertical: motion under gravity (acceleration = 9.8 m/s²)

Use x = v_xt for horizontal motion and

y = v_yt - (1/2)gt² for vertical motion.

Always start by drawing a diagram and identifying initial velocity, angle, and height. Then apply the kinematic equations separately for each direction.

These problems can seem tricky at first, but once you understand the setup, they follow predictable steps. I’ve helped many students get confident with these — let’s tackle it together!