What makes an object accelerate

Some students also strongly believe that this force is being used up if the object is slowing down. Students often struggle to grasp the concept of net force, and often think it is an extra force in addition to the actual forces on an object. The net force is the combined effect the sum of the real forces acting on the object. Net force is a valuable construct that has no separate existence of its own, unlike the real forces acting on the object, i.

While the net force on an object is zero, its speed and direction of motion remain unchanged and stationary objects remain stationary. When there is a net force on an object, it causes the object to accelerate in the direction of the net force; this is not the same as the direction of the motion unless the object is going in a straight line.

Explore the relationships between ideas about force and acceleration in the Concept Development Maps — Laws of Motion. The ideas about forces and motion below contribute to student understanding of this topic. These are each covered in greater detail in the sequence of teaching ideas introduced at the lower levels:. Students need exposure to situations that require verbal explanations about the forces involved before they are exposed to quantitative work involving formulae.

A simple mathematical relationship exists between the mass of an object m , the net force on the object f and its acceleration a. They can then be asked to identify all the actual forces and the net force on objects in a wide range of motion contexts. Some examples include: a ball rolling along a table; a ball that was rolling on a table but is now stopped; a ball thrown up in the air that is moving upwards or downwards ; a skateboard rider moving down a gently sloping path at a constant speed.

Isaac Newton's First Law of Motion states, "A body at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force. That situation is described by Newton's Second Law of Motion.

For a constant mass, force equals mass times acceleration. F is force, m is mass and a is acceleration. The math behind this is quite simple. If you double the force, you double the acceleration, but if you double the mass, you cut the acceleration in half. Newton expanded upon the earlier work of Galileo Galilei , who developed the first accurate laws of motion for masses, according to Greg Bothun, a physics professor at the University of Oregon.

Galileo's experiments showed that all bodies accelerate at the same rate regardless of size or mass. Newton also critiqued and expanded on the work of Rene Descartes, who also published a set of laws of nature in , two years after Newton was born. The submarine above has both vertical forces and horizontal forces acting on it. The horizontal forces will not affect its vertical movement and the vertical forces will not affect its horizontal movement.

The horizontal forces are equal in size and opposite in direction. They are balanced, so the horizontal resultant force is zero. This means that there is no horizontal acceleration. The vertical forces are equal in size and opposite in direction. They are balanced, so the vertical resultant force is also zero.

This means that there is no resultant vertical acceleration.