Lesson 2: Chapter 2 Laws of Motion

What is a song to help understand the 3rd law?

"If the _______(first object) exerts a force upon the _______(second object), then the _________ (second object) exerts a force upon the _________(first object); and they're* equal in strength and opposite in direction. They make a third law pair."

When is Newton's 2nd law of motion used?

- any time there is a net force (unbalanced force) - any time the motion of an object is changing (change in speed, direction, or both)

When does Newton's 1st law apply?

- if the total force on the object you are analyzing is zero - if the object is at rest - if the object is moving in a straight line and constant speed (uniform motion)

What are things to remember about the 3rd law?

- just because 2 forces are equal and opposite doesn't mean they are an interaction pair - 3rd law doesn't have anything to do w/the motion of an object (discusses the pair of forces in an interaction and measures the strength of a single interaction) - because forces come because of an interaction, the forces must be the same type of interaction (gravitational, contact, electric)

Force

- push or a pull that one object exerts upon another - anything that can cause an object to accelerate

Acceleration

- rate of change of velocity per unit time - change of velocity divided by the time required for the change - any change in velocity (speed and direction) of an object

Mass

- the characteristics of a body which determines how much it accelerates when a force is applied - tells you how easily it can be accelerated by a force

State of Uniform Motion

- the condition of an object when no unbalanced forces act upon it - a state of motion always refers to being at rest or in uniform motion

Centripetal Acceleration

- toward a center - acceleration at a right angle to an object's velocity

What are three things to remember w/Newton's 2nd law of motion?

1. stronger forces cause more acceleration 2. larger mass results in less acceleration 3. acceleration is in the direction of the net force

What is Newton's 3rd law of motion?

All forces result from interactions between pairs of objects, each object exerting a force on the other. The two resulting forces have the same strength and act in exactly opposite directions. for every action there is an equal and opposite reaction

A passenger in the Volkswagen is not wearing a seat belt. He is thrown toward the windshield. Which of the following is a correct explanation for this occurrence? A. The impact exerts a forward force on the occupants of the car. B. The car is still exerting a forward force on him for a short time after the accident, and this force propels him forward. C. The force of impact is backward, so there is an opposite and equal force forward on the occupants. D. He is not thrown forward. He just keeps moving in the direction he was originally going until something, like the windshield, stops him.

He is not thrown forward. He just keeps moving in the direction he was originally going until something, like the windshield, stops him.

Weight

a measure of the force of gravity pulling on an object

Interaction Pair

acts on a single pair of objects whose roles switch

What is Newton's first law of motion?

every object at rest, or in uniform motion, will remain in that state of motion unless compelled to do otherwise by forces acting upon it

Newton's 2nd Law of Motion

force = mass x acceleration (F=ma)

Uniform Motion

motion at a constant speed in a straight line

Suppose an elephant and an ant are both running at 1 mile per hour when they both encounter a long patch of slick ice where friction can be neglected. They begin to slide on the ice. Which of the following statements is true concerning their motion? A. The elephant will stop first due to its larger mass. B. The ant will stop first due to its smaller mass. C. The elephant and ant will stop at the same time. D. Neither the elephant nor the ant will stop and they will continue at 1 mile per hour as long as the ice lasts.

neither the elephant nor the ant will stop and they will continue at 1 mile per hour as long as the ice lasts

Is the hockey puck's motion dependent on the table's motion?

no

Velocity

speed in a particular direction of moving body

A driver in a Volkswagen bug (mass = 1335 kg) pulls out going 10 miles per hour in front of a Ford pickup truck (mass = 2675 kg) which is traveling 40 miles per hour. The two vehicles experience a head-on collision. Which of the following statements is true concerning the forces that each vehicle (and driver) experience in this collision? A. The Volkswagen bug experiences a much greater force than the Ford pickup truck due to the greater speed of the truck. B. The Volkswagen bug experiences a much greater force than the Ford pickup truck due to the larger mass of the truck. C. The Volkswagen bug experiences a force that is the same as the Ford pickup truck experiences D. The Volkswagen bug experiences a much smaller force than the Ford pickup truck due to the smaller speed of the Volkswagen bug. E. The Volkswagen bug experiences a much smaller force than the Ford pickup truck due to the smaller mass of the Volkswagen bug.

the Volkswagen bug experiences a force that is the same as the Ford pickup truck experiences

In this same head-on collision between the Volkswagen bug and the Ford pickup truck, which of the following statements is true concerning the acceleration of the pickup truck and Volkswagen bug? A. The acceleration of the truck is much greater than that of the Volkswagen bug. B. The acceleration of the truck is the same as that of the Volkswagen bug. C. The acceleration of the truck is much less than that of the Volkswagen bug. D. The truck experiences no acceleration but the Volkswagen bug experiences a large acceleration.

the acceleration of the truck is much less than that of the Volkswagen bug

Now two helpful Physical Science 100 students happen to see the plight of the elephant and the ant on the ice and decide to help them. The two students exert a force on the elephant of 1 N and a force on the ant of 1 N. Which of the following statements is true? A. The elephant will stop first due to its larger mass. B. The ant will stop first due to its smaller mass. C. The elephant and ant will stop at the same time. D. Neither the elephant nor the ant will not stop and will continue at 1 mile per hour as long as the ice lasts.

the ant will stop first due to its smaller mass

What can you determine about the masses of the balls? A. The ball with the most mass accelerated the most. B. The ball with the least mass accelerated the most. C. Nothing can be determined about the masses.

the ball with the least mass accelerated the most

In which of the following situations is the car accelerating? A. The car is accelerating in all of the situations below. B. The car is accelerating when it travels different distances in the same amount of time. C. The car is accelerating when it goes around a curve at constant speed. D. The car is accelerating when it goes over a hill at constant speed. E. The car is accelerating when it is sitting still on the planet Earth.

the car is accelerating in all of the situations below

Imagine a man standing on the floor. What is the "reaction" force (the second force required by the Third Law of Motion) to the man's weight? (Plug the two objects involved into the song if it helps.) Here are your choices: (Click on your choice to see if you are correct.) A. The force the man exerts on the ground. B. The force the man exerts on the earth. C. The force the ground exerts on the man. D. The force the earth exerts on the man.

the force the man exerts on the earth

If the air table was turned off so that friction between the air table and the hockey puck become significant, how would you describe the motion of the puck when the air table turned left? A. The hockey puck would have continued in a straight line as it did when the air table was turned on B. The hockey puck would have turned to the right. C. The hockey puck would have turned to the left. D. The hockey puck would have sped up but stayed in a straight line.

the hockey puck would have turned to the left

Is the hockey puck's motion at a constant speed?

yes

Is the hockey puck's motion consistent with Newton's 1st Law of Motion?

yes

Is the hockey puck's motion in a constant direction?

yes