Motion - Chapter 8.1 Speed Velocity Momentum

Speed Distance traveled divided by the time during which motion occurred Constant speed means that an object travels the same distance in the same amount of time Objects at rest have a speed of 0 m/s

Speed Equation Distance Time Speed = v = d t

Speed Example Suppose a wheelchair racer finishes a 132 m race in 18 s. What was the racer’s average speed?

Speed Example Distance = 132 meters Time = 18 seconds Speed = 132 meters/18 seconds Speed = 7.3 m/s

Velocity Quantity describing both speed and direction Same calculation as speed except that it also designates a direction. It may be designated as north, south, east, west, or positive or negative.

Are speed and velocity the same? A car travels at a constant speed of 30 miles/hour. The car makes a left at a speed of 30 miles /hour. Speed did not change Velocity did change

Velocity Example Find the velocity of a swimmer who swims exactly 110 m toward the shore in 72 s.

Velocity Example Distance = 110 meters Time = 72 seconds Speed = 110 meters/72 seconds Speed = 1.5 m/s Velocity = 1.5 m/s towards the shore

November 18, Do Now: In written format, explain the difference between speed and velocity. Give an example of each.

Momentum A quantity defined as the product of an object’s mass and its velocity The greater the mass or the faster the velocity, the greater the momentum

Momentum Equation Momentum = mass x velocity Equation is p=mv P is used to represent momentum

Momentum Example Find the momentum of a 75 kg speed skater moving forward at 16 m/s.

Momentum Example Mass = 75 kilograms Velocity = 16 m/s forward Momentum = (75 kg)(16m/s) Momentum= 1200 kg m/s forward

Conservation of Momentum The total amount of momentum in a system is conserved If two vehicles with different masses are traveling with different velocities and they hit head on, the momentum of the two cars before the collision is the same after the collision.

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Acceleration and Force - Chapter 8.2 Acceleration Force Friction and Air-resistance Gravity

Acceleration change in velocity divided by the time in which the change occurred The greater the acceleration the faster the object is speeding up.

Acceleration If the speed remains constant, acceleration is zero. SI unit is meter/second per second (m/s 2 )

Acceleration Equation velocity Time Acceleration = a = v t

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Acceleration Example Find the acceleration of a northbound subway train that slows down from 12 m/s to 9.6 m/s in 0.8 s.

Acceleration Example Initial Velocity = 12 m/s Final Velocity = 9.6 m/s Time = 0.8 seconds Acceleration = (9.6 – 12m/s)/0.8s Acceleration = -3 m/s 2

November 20, 2015 Objective: Predict how an applied force can affect an object’s motion. Homework: Study Quizlet set (test has to be 80%). Acceleration and Force #4-5 and Acceleration and Gravity #3-5 worksheets. Do Now: Write the letter formula/equation and units for 1. Velocity 2. Speed 3. Momentum 4. Acceleration

Force The cause of acceleration or the change in an object’s velocity SI unit of force is a newton. (N) F = mass x acceleration HGk HGk

Force Balanced forces do not change motion Unbalanced forces result in a net movement in one direction. This occurs because the net force on one side is less than the net force on the other. Tug of War.

Friction the force between two objects in contact that opposes the motion of either object friction maintains balanced forces

Air Resistance Air resistance is a form of friction Air resistance is increased by the size of the object in motion or the speed that it travels

Gravity This is the attraction between two particles of matter due to their mass. Gravitational force is also determined by the distance between the two masses.

November 20, 2015 Objective: Analyze the relationships of mass, acceleration, and force. Do Now: If the acceleration speed remains constant, then a=? What is the SI unit for acceleration? What does the “delta” (∆) symbol stand for?

Laws of Motion - Chapter 8.3 Newton’s 1 st Law Newton’s 2 nd Law Newton’s 3 rd Law

Newton’s 1 st Law An object at rest remains at rest and an object in motion maintains its velocity unless it experiences an unbalanced force. Inertia w w

Newton’s 2 nd Law The unbalanced force acting on an object equals the object’s mass times its acceleration. F=ma

Measuring Force Force is measured in newtons. 1 N=1 kg x m/s 2 1 lb=4.448 N 1 N=0.225 lbs

Force Example What is the force necessary for a kg automobile to accelerate forward at 2.0 m/s 2 ?

Force Example Mass = kg Acceleration = 2.0 m/s 2 Force = (16000 kg)(2.0 m/s 2 ) Force = N

Free Fall the motion of a body when only the force of gravity is acting on it. Acceleration of gravity is 9.8m/s 2 Everything will fall at this acceleration

Mass vs. Weight Mass represents the measured amount of matter in an object. Weight is the gravitational force an objects experiences based on its mass. Weight = mass x gravity w=mg, weight is a force.

Terminal Velocity The maximum velocity reached by a falling object. This occurs when air resistance is equal to the force due to gravity. Terminal Velocity of a skydiver is ~200 miles/hr

Newton’s third Law For every action there is an equal and opposite reaction Rockets move as a result of action and reaction.

November 23, 2015 Objective: Do Now: ID Newton’s Laws: 1. The unbalanced force acting on an object equals the object’s mass times its acceleration=___________law 2. For every action there is an equal and opposite reaction =_____________ law 3. An object at rest remains at rest and an object in motion maintains its velocity unless it experiences an unbalanced force.=______________law