Newton´s Laws of Motion

After Newton established the three Newton’s laws of motion; the way people saw the motion of the objects was change.

Let start knowing a little about Sir Isaac Newton.

There was this fellow in England named Sir Isaac Newton, one of the greatest scientists and mathematicians that ever lived. A little bit stuffy, bad hair, but quite an intelligent guy. He worked on developing calculus and physics at the same time.

Sir He was born in England on December 25, 1643. He was born the same year that Galileo died. He lived for 85 years.

Isaac Newton was raised by his grandmother. He attended Free Grammar School and then went on to Trinity College Cambridge. Newton worked his way through college. While at college he became interested in math, physics, and astronomy. Newton received both a bachelors and masters degree. While Newton was in college he was writing his ideas in a journal. Newton had new ideas about motion, gravity, the diffraction of light, and forces. Newton's ideas were so good that Queen Anne knighted him in 1705. His accomplishments laid the foundations for modern science and revolutionized the world. Sir Isaac Newton died in 1727.

During his work, he came up with the three basic ideas that are applied to the physics of most motion (NOT modern physics). 

The ideas have been tested and verified so many times over the years, that scientists now call them Newton's Three Laws of Motion. 

Newton´s 1^st law of motion

¨An object at rest will remain at rest unless unbalanced forces acted on it, and an object in motion will continuous moving with a constant velocity and in a straight line unless unbalanced forces acted on it¨

Motion (or lack of motion) cannot change without unbalanced force acting. If nothing is happening to you, and nothing does happen, you will never go anywhere. If you're going in a specific direction, unless something happens to you, you will always go in that direction. Forever. 

This law sometimes is called law of Inertia. Inertia is the capacity of all the objects to resist any changes in motion. In other words:

This law is the same reason why you should always wear your seatbelt.

Newton´s 2^nd law of motion

¨"The acceleration of an object depends on the mass of the object an the amount of force applied"

Everyone unconsciously knows the Second Law. Everyone knows that heavier objects require more force to move the same distance as lighter objects.

This law permits us to calculate the force required moving objects, or the acceleration of an object after a force acted on it.

This law can be written as:

a=F/m

a is acceleration in m/s²

F is net force in N

m is mass in kg

We can use this equation to calculate Force or mass, using the triangle to clearway the unknown. Remember for use the triangle you just have to cover the unknown and you will obtain the formula that you need.

Newton´s 3^rd law of motion

¨Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. For every action there is an equal and opposite reaction¨

This means that for every force there is a reaction force that is equal in size, but opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the opposite direction equally hard. Forces are found in pairs.

Think about the time you sit in a chair. Your body exerts a force downward and that chair needs to exert an equal force upward or the chair will collapse. It's an issue of symmetry. Acting forces encounter other forces in the opposite direction. There's also the example of shooting a cannonball. When the cannonball is fired through the air (by the explosion), the cannon is pushed backward. The force pushing the ball out was equal to the force pushing the cannon back, but the effect on the cannon is less noticeable because it has a much larger mass. That example is similar to the kick when a gun fires a bullet forward. 

This law is exemplified by what happens if we step off a boat onto the bank of a lake: as we move in the direction of the shore, the boat tends to move in the opposite direction (leaving us facedown in the water, if we aren't careful!).

I. Solve the following problems

1. What net force is required to accelerate a car at a rate of 2 m/s² if the car has a mass of 3,000 kg?

 2. A10 kg bowling ball would require what force to accelerate down an alleyway at a rate of 3 m/s²?

3. Sally has a car that accelerates at 5 m/s². If the car has a mass of 1000 kg, how much force does the car produce?

4. What is the mass of a falling rock if it produces a force of 147 N?

5. What is the mass of a truck if it produces a force of 14,000 N while accelerating at a rate of 5 m/s² ?

6. What is the acceleration of softball if it has a mass of 0.5 kg and hits the catcher's glove with a force of 25 N?

7. Your own car has a mass of 2000 kg. If your car produces a force of 5000 N, how fast will it accelerate?

8. Sally wants to accelerate even faster than in problem #3, so she removes 500 kg of mass from her car. How fast will her 1500 kg car accelerate if it produces 5000 N of force?

9. Sally challenges you to a race. On the first turn you run off the course and your car strikes a large bale of hay. Your car still produces 5000 N of force, but now it accelerates at only 2 m/s². What is the mass of your car now that the bale of hay is stuck to it?

10. Even tough she is way ahead of you, Sally switches her car to run on nitrous oxide fuel. The nitrous oxide allows her car to develop 10,000 N of force. What is Sally's acceleration if her car has a mass of 500 kg?

II. Write the term that matches each description in items 1 through 6 below on the spaces provided.

Unscramble the boxed letters to spell the term that answers question 7.

			1
					2
3
							4
				5
		6

1. A measure of an object’s tendency to remain at rest or continue at constant speed

2. How far something travels

3. How far something ends up from its starting place

4. A push or a pull

5. Forces that result in no change in an object’s motion

6. The force that resists motion

7. An object will remain at rest or move in a straight line with constant speed unless it is acted upon by a force. This is the definition of Newton’s first law of

III. Give three daily examples for daily applications for each one of the three Newton´s laws of motion.

IV. Use Newton´s 3^rd law of motion to explain why your foot hurt after you kick a rock

V. What is inertia?      

VI. Rockets make use of Newton’s third law of motion. What is that law?

VII. A spacecraft traveling through space can travel at a constant speed and in a straight path without using engines. Why?