Which law answers

The mass and velocity of the airplane change during the flight to values m1 and V1. Let us assume that the mass stays a constant value equal to m. The weight of the fuel is probably small relative to the weight of the rest of the airplane, especially if we only look at small changes in time.

If we were discussing the flight of a baseball , then certainly the mass remains a constant. But if we were discussing the flight of a bottle rocket , then the mass does not remain a constant and we can only look at changes in momentum. The change in velocity divided by the change in time is the definition of the acceleration a. The second law then reduces to the more familiar product of a mass and an acceleration:.

Remember that this relation is only good for objects that have a constant mass. This equation tells us that an object subjected to an external force will accelerate and that the amount of the acceleration is proportional to the size of the force. The amount of acceleration is also inversely proportional to the mass of the object; for equal forces, a heavier object will experience less acceleration than a lighter object.

Considering the momentum equation, a force causes a change in velocity; and likewise, a change in velocity generates a force.

The equation works both ways. The velocity, force, acceleration, and momentum have both a magnitude and a direction associated with them. Scientists and mathematicians call this a vector quantity.

Both the mathematical equation and physical examples are discussed, including Atwood's Machine to illustrate the principle. Students come to understand that an object's acceleration depends on its mass and the str Students should be familiar with the concepts of mass, properties of matter weight, density, volume , and basic algebraic equations. Newton's third law of motion builds further on the first and second laws of motion. The third law of motion states that for every action, there is an equal and opposite reaction.

This can be observed both in objects at rest and those that are accelerating. For example, a resting box pushes down on the ground due to a gravitational force. In reaction to this, the ground presses back up, what we call a "normal force," at an equal magnitude.

These forces balance so no acceleration of the box occurs. Newton's third law can also be observed in rockets and other projectiles. To launch, a large force is exerted from the engines of a rocket on the space behind it. In reaction to this force, the air pushes back with an equal magnitude, propelling the rocket forward.

What other examples can you think of? Continue by showing the presentation and delivering the content in the Lesson Background section. Open the Forces and Newton's Third Law Presentation for all students to view and present the lesson content, guided by the script below and text in the slide notes. Ask students: Have you heard this before?

What do you think it means? Then demonstrate the third law by showing students a modern version of Hero's Engine, which takes just a few minutes. Hero of Alexandria was an ancient Greek mathematician and experimentalist who lived in Egypt. His original engine was steam-powered, but the soda can version works well to demonstrate the same concept.

For the demo, fill the prepared can with water and lift it with the string over a sink or tub or outside so students can observe the rotational movement as water flows out of the holes and the can spins. The can spins due to the reaction force associated with the flow of water. Alternatively, demonstrate the third law by having one student sit on a scooter with a basketball and then throw the ball to another student.

The reaction force from the throw is evident when the throwing student is propelled backward on the scooter. Identify the action-reaction pair for the class: the block's weight pushes on the ground and the ground pushes back up on the block.

The cannon exerts a force on the cannon ball, and the cannon ball exerts an equal and opposite force on the cannon. Point out that Newton's third law explains the recoil of projectile weapons such as cannons and guns. Students who have seen Wall-E may recall a scene in which the robot uses the fire extinguisher as a propulsion system the reaction force causes the robot to move.

The space shuttle exerts a downward force, and the reaction force pushes it upwards. Examples: hand-helmet, hand-shoulder, ball-hand, shoe-ground. This may be a good time to review how to draw conceptual free-body diagram vectors arrows of force, velocity and acceleration.

Conclude the presentation with a review of the key concepts, as listed on the slide, with blanks for students to supply the answers. Through these three lessons, expect students to have developed an understanding of Isaac Newton's three laws of motion. These fundamental laws of physics describe how forces impact the motion of objects. Without forces, no changes in motion can occur. Understanding forces can be a very powerful thing! Because engineers understand how forces cause objects to slow down, speed up and turn, they are able to design complicated mechanical systems ranging from airplanes to door knobs to delicate drug delivery systems.

Next, conduct the associated activity, Sliding Textbooks , followed by the final quiz, as described in the Assessment section. Newton's first law: Unless an unbalanced force acts on an object, an object at rest stays at rest and an object in motion stays in motion. Newton's third law: For every action, there is an equal and opposite reaction. Verify that students are confident with Newton's first and second laws before continuing with Newton's third law. Questions: As an embedded assessment, gauge student understanding of Newton's third law based on their responses to the questions on slides 4, 5 and 6 of the Forces and Newton's Third Law Presentation.

Use the questions on slide 7 as a review prior to administering the final quiz. Unit Quiz: After reviewing the questions on slide 7, answering any remaining student questions and conducting the associated activity, Sliding Textbooks , administer Newton's Laws Final Quiz as an assessment that covers the material in all three lessons in the unit.

Consistent with the above equation, a unit of force is equal to a unit of mass times a unit of acceleration. By substituting standard metric units for force, mass, and acceleration into the above equation, the following unit equivalency can be written. The definition of the standard metric unit of force is stated by the above equation. The table below can be filled by substituting into the equation and solving for the unknown quantity.

Try it yourself and then use the click on the buttons to view the answers. The numerical information in the table above demonstrates some important qualitative relationships between force, mass, and acceleration. Comparing the values in rows 1 and 2, it can be seen that a doubling of the net force results in a doubling of the acceleration if mass is held constant. Similarly, comparing the values in rows 2 and 4 demonstrates that a halving of the net force results in a halving of the acceleration if mass is held constant.

Acceleration is directly proportional to net force. Furthermore, the qualitative relationship between mass and acceleration can be seen by a comparison of the numerical values in the above table. Observe from rows 2 and 3 that a doubling of the mass results in a halving of the acceleration if force is held constant. And similarly, rows 4 and 5 show that a halving of the mass results in a doubling of the acceleration if force is held constant. Acceleration is inversely proportional to mass.

Whatever alteration is made of the net force, the same change will occur with the acceleration. Double, triple or quadruple the net force, and the acceleration will do the same. On the other hand, whatever alteration is made of the mass, the opposite or inverse change will occur with the acceleration. Double, triple or quadruple the mass, and the acceleration will be one-half, one-third or one-fourth its original value. As stated above , the direction of the net force is in the same direction as the acceleration.

Thus, if the direction of the acceleration is known, then the direction of the net force is also known. Consider the two oil drop diagrams below for an acceleration of a car. From the diagram, determine the direction of the net force that is acting upon the car.

Then click the buttons to view the answers.