Skip to Content Go to sign in Skip to Primary Navigation Skip to Secondary Navigation Skip to Page Navigation Skip to Header Navigation Skip to Footer Navigation Read more about accessability options and our navigation

Physics Classroom is making strides to make our site accessible to everyone. Our site contains 6 navigation areas. The Primary, Secondary, and Page Level navigations have a screen reader version of their nav structure that allows using the left and right keys to navigate sibling navigation items, and up or down keys to navigate parent or child navigation items. The others can be navigated using tabs. The Primary Navigation handles the first 2 levels of site pages. The Secondary (which is not always available) handles the 3rd and 4th level of structure. The Page level navigation allows you to navigate the current page's headings quickly. The Header Navigation contains the Light/Dark Mode toggle, Search, Notifications and account login. The Breadcrumb Navigation contains the breadcrumb of the current page. If the current page has a breadcrumb, you can get to it by skipping to the content and tabbing in reverse (shift plus tab). The Footer Navigation contains links such as Privacy, Contact, about and terms. Some resources contain an Audio Player that can be activated by holding down the T key for 3 seconds, and then using K to pause and resume. While not every area of Physics Classroom is usable purely from keyboard and screen reader, we are committed to continue work on making this possible. If you have questions or need additional help, please use this link to contact us.

Return to screen reader navigation

Mission VP8 Velocity and Acceleration of a Projectile

 The Question

The acceleration of a projectile is always directed ...

 Define Help

Definition of a Projectile:
A projectile is an object for which the only force acting upon it is gravity. The force of air resistance is negligibly small or nonexistent for a projectile.

 Think About It

Forces, when unbalanced, cause objects to accelerate; and the direction of the acceleration is in the same direction as the unbalanced force. A projectile is an object acted upon by a single force - the force of gravity. Being a downward force, gravity accelerates projectiles in the ____ direction. (It is your job to reason from the previous statements, the word that fills in the blank.)

 Don't be Fooled

Many students confuse velocity and acceleration. One misconception a student has is related to the direction of the acceleration, thinking that it is in the same direction that the object moves. But don't be fooled! This is not always the case.

Both velocity and acceleration are vectors; both have a direction associated with them. The direction of the velocity vector is in the same direction that the object moves. Yet the direction of the acceleration vector can be in the same or the opposite direction that the object moves, depending on whether there is a speeding up motion or a slowing down motion. If an object slows down, the direction of the acceleration is opposite the direction that the object is moving.

Return to Screen Reader Navigation