# Newtons first law REVIEW Summarize what the law

• Slides: 13

Newton’s first law REVIEW Summarize what the law states. What does an object at rest need for it to move? What is another name for newton’s first law of motion? What is inertia? What causes a moving object to stop moving? The (more/less) mass an object has, the harder it is to move.

Newton’s Second Law

NEWTON’S second law The acceleration of an object depends on the mass of the object and the amount of force applied. VOLUNTEERS!!!!! TWO “pushers” of similar size ONE small 8 th grader ONE big 8 th grader

Part 1: Acceleration depends on mass Acceleration of an object decreases as its mass increases Acceleration of an object increases as its mass decreases Which would be easier to push? WHY?

Part 2: Acceleration depends on force Acceleration of an object increases as the force on it increases Acceleration of an object decreases as the force on it decreases VOLUNTEERS!!!!! ONE to sit in chair ONE to push chair

Newton’s law with MATH Formula: acceleratio n a= F m Force mass UNITS acceleration: m/s² (meters per second squared) force: N mass: kg (Newtons) (kilograms)

Tricky…tricky…. �You don’t use newtons to find acceleration in this formula 1 N = 1 kg∙m/s² So… 4 N = 4 kg∙m/s² And…. 500 N = 500 kg∙m/s² And 395 N = ?

Newton and math example Mass of apple: 0. 102 kg Force: 1 N Acceleration? a= 1 kg∙m/s² (1 N)/ 0. 192 kg a= 9. 8 m/s

Practice What is the acceleration of a 3 kg mass if a force of 14. 4 N is used to move the mass?

Practice 2 What is the acceleration of a 7 kg mass if a force of 68. 6 N I used to move it toward earth?

Challenge question What force is necessary to accelerate a 1, 250 kg car at a rate of 40 m/s² ? HINT: F = m x a

Another challenging question Zookeepers carry a stretcher that holds a sleeping lion. The total mass of the lion and the stretcher is 175 kg. The lion’s forward acceleration is 2 m/s². what is the force necessary to produce this acceleration?

Newton’s Laws video clip �CLIP