2.2 – Force and Mass Determine Acceleration

Newton’s second law relates force, mass, and acceleration Acceleration increases as force increases and decreases as mass increases Direction an object accelerates is the same as the force

If you pushed two objects of different masses with the same amount of force, the object with less mass would accelerate more The softball would accelerate more because it has less mass

Force equals mass times acceleration You can calculate one of the factors if you know the other two. Newton is the standard unit of force (1 kg · m/s²). Above is the mathematical form of Newton’s Second Law.

Sample Problem Using Newton’s Second Law If a 5 kg ball is accelerating 1.2 m/s², what is the force on it? F = (5 kg) (1.2 m/s²) F = 6 kg · m/s² F = 6 N

Mass & acceleration Mass is a variable in Newton’s Second Law If the same force acts on two objects, the object with less mass will have the greater acceleration. If objects lose mass, they gain acceleration if the force remains the same.

As the space shuttle takes off, it’s thrust is the same throughout the whole lift-off. However, the mass decreases due to fuel burning resulting in increased acceleration.

Forces can change the direction of motion Newton’s Second Law says that if you apply a force to an object, it will accelerate in the direction of the force. The swings are constantly accelerating because they are constantly changing direction.

Centripetal force A force that keeps an object moving in a circle Points towards the center of the circle Stops an object from going in a straight line

The centripetal force applied in this “around the world” trick is always in the direction of the string. Towards the performer.

Circular motion and Newton’s second law Which requires more centripetal force? If the hammer thrower increased his acceleration, what would happen to the centripetal force?