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
Home Concept Builders Momentum, Collisions and Explosions Hit and Stick Collisions - Law Enforcement Directions

Hit and Stick Collisions - Law Enforcement - Directions

Using the Hit-and-Stick Collisions - Law Enforcement Concept Builder is quite simple. There are three different difficulty levels. Difficulty levels differ only in terms of the number of question presented to students. As you progress through any of the difficulty levels, you will be presented with a queston that you will have to answer. The question presents three situations involving the collision of a moving object with a stationary object; the two objects stick together and move at the same speed after the collision. A Before-Collision and an After-Collision representation of the mass and velocity of each is presented. You will have to determine which of the three situtations violate the law of conservation of momentum. Tap on any situation that does. Once you tap on one or more situations, they will be displayed behind bars (since they break the law of momentum conservation) and a Check Answer button appears. Once you are satisfied with your answer, tap on the Check Answer button. Your answer will be evaluated and your Progress Report will be updated.

The diagrams show a cart that may or may not be loaded with bricks. Each brick has the same mass as a cart. And so a cart with a brick on it has twice the mass as an unloaded cart. And a cart loaded with two bricks has three times the mass as an unloaded cart.


The diagrams also show velocity vectors for the two carts in the After Collision diagram. The length of the arrow is proportional to the velocity. The arrow lengths are either 1-unit long, 2-units long, 3-units long, 4-units long, or 5-units long.



By making careful observations of the mass and velocity information, and by using a momentum formula, you will be able to determine if the After Collision momentum of the system is the same as or different than the Before Collision momentum of the system.



Your goal is to earn "Stars" and to complete one or more difficulty levels. Stars are earned when you demonstrate success with a particular question. Once you show success on all the Question Groups at a particular difficulty level, you will earn the reward for that difficulty level.

Concept Builder Teacher Notes