Motion Motion When an object changes position over
Motion
Motion When an object changes position over time from one spot to another. Reference point: Is a place or object used for comparison to help to determine motion. Use non-moving objects such as trees, buildings, or mountains.
Speed Objects in motion have speed. Speed is the distance the object travels per unit of time. If we know the distance and how long it takes (time), we can find the speed. Units used: meters per second (m/s) Formula: Speed = Distance Time
Practice: Calculating Speed Kira jogs to a store 72 m away in a time of 36 s. What is Kira’s average speed?
Practice: Calculating Speed An airplane traveling from San Francisco to Chicago travels 1, 260 km in 3. 5 h. What is the airplane’s average speed?
Practice: Calculating Distance An athlete swims a from one end of a pool to the other end in a time of 25 s and at a speed of 2 m/s. What distance did the athlete travel?
Distance The length of the path between two points. Point A Point B We can also find the distance if you take the time traveled & the speed and multiply them together. Distance = speed x time
Velocity To describe an object’s motion completely we also need to know the direction of its motion. Velocity is both the speed and the direction the object is traveling. Don’t get speed & velocity confused Velocity MUST include a reference direction. Velocity changes when your speed changes and/or your direction changes.
In your own words! Explain the difference between speed & velocity.
How can you graph motion? To show motion on a graph, you can use a line graph. Time is shown on the horizontal axis (x-axis) Distance is shown on the vertical axis (y-axis) The steepness of the line is called the slope. Slope tells you the rate of change.
Acceleration Is the rate at which velocity changes. It can change by increasing speed, decreasing speed, or changing direction. The faster velocity changes, the greater the acceleration change. Acceleration Equation (final velocity)-(starting velocity) Acceleration = Change in time
Try This!! As a roller coaster car starts down a slope, its speed is 4 m/s, but 3 seconds later, at the bottom, its speed is 22 m/s what is its average acceleration? final velocity initial velocity time Acceleration= --------------------22 m/s 4 m/s 3 s Acceleration = ----------18 m/s 3 s Acceleration = ------6 m/s 2 Acceleration =
Practice: Calculating Acceleration What is the average acceleration of a subway train that speeds up from 9. 6 m/s to 12 m/s in 0. 8 s on a straight section of track?
Momentum Depends on the object’s mass and velocity. The more momentum an object has the harder it is to stop the object or change its direction. Calculating Momentum: Momentum (p) = mass x velocity
Practice: Calculating Momentum What is the momentum of an ostrich with a mass of 120 kg that runs with a velocity of 16 m/s north?
Practice: Calculating Momentum What is the momentum of a 6 kg bowling ball that is moving at 10 m/s down the alley toward the pins?
Newton’s Laws of Motion Who was Newton? Sir Isaac Newton was an English physicist and mathematician. He studied the changes in the motion of objects and gave us 3 laws to explain motion.
Newton’s 1 st Law of Motion An object at rest remains at rest, and an object in motion remains in motion unless acted on by an outside (unbalanced) force. This law is also known as the “ Law of Inertia” Inertia – is the tendency of all objects to resist any change in motion. If the object is at rest, it is resistant to move. If the object is moving it is resistant to change speed or directions.
Mass and Inertia Mass is a measure of inertia. Mass Is the measurement of “stuff” in an object. The amount of “stuff” doesn’t change. An object that has a small mass has less inertia than object that a large mass. Changing the motion of an object that has a small mass is easier than changing the motion of an object that has a large mass.
2 nd Law of Motion The acceleration of an object depends on the mass of the object and the amount of force applied. This law describes the motion of an object when an unbalance force acts on an object.
Newton’s 2 nd Law has 2 parts 1. Acceleration Depends on mass. Acceleration of an object increases as its mass decreases. (smaller objects can accelerate faster than bigger objects) Acceleration of an object decreases as it mass increases. (bigger objects have a harder time accelerating) 2. Acceleration depends on force. Acceleration of an object is always in the same direction as the force applied. (object goes in the same direction as it was pushed or pulled)
Newton’s Law Mathematically To find acceleration: Acceleration = force mas s We can rearrange the equation to find force: Force = acceleration x mass
Practice: Calculating Acceleration What is the acceleration of a 7 kg mass if a force of 68. 6 N is used to move it towards the earth?
Practice: Calculating Force 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/s 2. What is the force necessary to produce this acceleration?
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. Simply stated: All forces act in pairs. If a force is exerted, another force occurs that is equal in size and opposite in direction. When a force is exerted there is always a reaction force. A force NEVER acts by itself.
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