CHAPTER 6: Forces in motion
Summery
Chapter 6 talks about how forces are affected by gravity,motion, and air resistance. Newtons laws explain this throughout the chapter.
SECTION 1: GRAVITY AND MOTION
VOCABULARY
1.) Terminal velocity: the constant velocity of falling object when the force of air resistance is equal in magnitude and opposite direction to the force of gravity
2.) Free fall: the motion of a body when only the force of gravity is acting on the body
3.) Projectile motion: the curved path that an object follows when thrown, launched, or otherwise projected near the surface of earth
2.) Free fall: the motion of a body when only the force of gravity is acting on the body
3.) Projectile motion: the curved path that an object follows when thrown, launched, or otherwise projected near the surface of earth
SUMMERY OF SECTION 1: GRAVITY AND MOTION
In the late 1500's a young Italian scientist Galileo questioned Aristotle's idea about falling about falling objects. He dropped two cannon balls of different masses from the top of the Leaning Tower of Pisa in Italy. They fell to the ground at the same time. Objects fall at the ground at the same rate because the acceleration due to gravity is the same for all objects. Acceleration is the rate at which velocity changes over time. All objects accelerate toward earth at a rate of 9.8 m/s, so you can calculate the change in velocity of a falling object using; volume= gravity x time. The force of gravity may pull downward but air resistance pushes upward, because air resistance is the force that opposes motion of objects through the air. Another type of motion includes free fall, but free fall can only occur when there is no air. A type motion that is commonly used in today's world and thousands of years include projectile motion. Projectile motion has two components horizontal motion and vertical motion. Examples of projectile motion include; a frog leaping, water sprayed by a sprinkler, or balls being juggled.
AIR RESISTANCE
The picture shows an example of air resistance with the parachute resisting air flow from above and gravity from below to reach terminal velocity.
Section 2: Newtons law of Motion
VOCABULARY
1.) Inertia: the tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction until an outside force acts on the object.
Summary
In 1686, Sir Issac Newton explained the relationship between force and the motion of an object with his three laws of motion. There are three laws of motion that explain motion and force. Newtons first law of motion explains this; An object at rest remains at rest, and an object in motion remains in motion at a constant speed and in a straight line unless acted on by an unbalanced force. Basically what this law is saying is that an object will stay at rest until it another force acts upon it, and an object in motion will stay in motion until another force acts upon it. Newtons second law of motion explains this; The acceleration of an object and the amount of force applied. This law is basically saying that the bigger the object the harder it is to get it to start moving, and the harder it is to stop. You can express Newtons second law mathematically by this formula; f/m, or force= mass x area. Newtons third law of motion talks about force. This is what it really says; Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. This law is basically saying that all forces act in pairs. Some examples of action and reaction pairs include this; space shuttle thrusters, rabbits legs, and also a bat and a ball.
Objects in motion
This picture shows a fighter jet in motion.
Objects in motion
This picture is showing objects in motion, because the balls were falling. From an upward ledge or surface.
Section 3: Momentum
VOCABULARY
1.) Momentum: a quantity defined as the product of the mass and velocity of an object
Summary
The momentum of an depends on its mass and velocity. The momentum an object has, the harder it is to stop the object or change its direction. You can calculate momentum with this equation; momentum(p)= mass x velocity. The Law of Conservation of Momentum states that when a moving object hits another object, some or all of the momentum of the first object is transferred to the object that is hit. That basically means is that when objects collide the total amount of momentum stays the same. Sometimes two objects stick together after a collision, after two objects stick together they move as one object. The combined objects move in the direction of the object that had the greater momentum before the collision. So, when mass changes, the velocity must change , too. In other collisions the objects bounce off each other. During these types of collisions, momentum is usually transferred from one object to another object. The transfer of momentum causes the objects to move in different directions at different speeds.
MOMENTUM
In this photo shows how momentum is transferred from one object to another. The player has trucked the other causing more momentum to be transferred to the second object. Click here for more