Force & Motion

Newton's 2nd Law

Newton's 2nd Law is the idea that the acceleration of an object is dependent on the net force applied to the object and the mass of the object. The equation for Newton's 2nd Law is Force = Mass x Acceleration.

For example, if a 20 gram toy car accelerates at 10 m/s² the force applied would have to be 200 Newtons of Force. 200 N = 20 g x 10 m/s².

This also means that if you used more force, like say 300 Newtons, the acceleration of the toy car would increase to 15 m/s². 300 N = 20 g x 15 m/s².

If you increase the mass to 40 grams rather than increasing the force, the acceleration would decrease to 5 m/s². 200 N = 40 g x 5 m/s².

Newton's 3 Laws of Motion

Newton's three laws of motion are called the Law of Inertia (1st Law), the Law of Acceleration (2nd Law), and the Law of Action and Reaction (3rd Law).

Newton's 1st Law states that an object at rest will stay at rest, and an object in motion will stay in motion, unless acted upon by an unbalanced force. This is because of inertia which is the tendency for an object to resist a change in motion.

The more mass an object has, the more inertia it has.

Newton's 2nd Law states the acceleration of an object is directly dependent on the net force applied to the object and the mass of the object.

Newton's 3rd Law states that for every action, there is an equal and opposite reaction.

1st Law : The ball is at rest continues to stay at rest until Bob kicks it. Since the ball has a relatively small mass, its inertia is smaller which makes it easier for Bob to kick.

2nd Law : Bob kicks the ball which causes to quickly accelerate in the direction he applied the force.

3rd Law : Every force acting on the ball has an equal and opposite reaction. Gravity pushes the ball down while normal force pushes the ball up. The applied force of Bob's kick pushes the ball to the left while friction acts in the opposite direction of the applied force of Bob's kick. The normal force and gravity are equal in force. The applied force and friction are also equal in force.

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