The New Alison App has just launched Download Now

Physics Normal and Contact Forces - Revised

Gain a better understanding of Newton's first law of motion, gravity, normal force, and friction with this course.

Teaching & Academics
Free Course
This free online physics course will give you a better understanding of the force of gravity and its counterpart, the normal force. By the end of the course you will have learned why some objects do not move even when they are on a slope, and will understand the effects different forces have on objects. Did you know that when you try to move a heavy object, it takes more effort to get it moving than to keep it moving? Learn why, today.
  • Duration

    1.5-3 Hours
  • Certification

  • Mobile Friendly

  • Publisher

    Khan Academy
  • Accreditation






View course modules


Newton's first law states that an object at rest will stay at rest while an object in motion will stay in motion unless there is some unbalanced or net force. This course will first introduce you to a normal force which is the force when an object is resting on any surface that is perpendicular to the surface of the object. You will learn that if two surfaces are not in contact, they can't exert a normal force on each other.

Gravity decreases in strength the further you move away from the center of the earth. This course will discuss the force of gravity which is equal to mass times the gravitational field of the earth, about 9.8 meters per second. You will learn that a net force is mass times acceleration, and that to calculate the rate acceleration of an object, you divide the force of the direction it’s moving by the mass of the object. You will also study kinetic friction and static friction.

Kinetic friction is a force that acts between moving surfaces and static friction is a force that keeps an object at rest. By taking this course, you will learn how to calculate the static and kinetic friction on a stationary object to be moved along a surface. So, check out the course and start learning about the dynamics of moving objects on specific surfaces, today.

Start Course Now