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# Physics Talk 2.3 - PowerPoint PPT Presentation

Physics Talk 2.3. Newton’s Second Law. September 30 , 2013 HW: . Do Now: Copy LO and SC Agenda: Do Now LO and SC Investigate Physics Talk, Notes Active Physics Plus. Learning Objective: Students use F=ma to solve problems relating to Newton’s Second Law of Motion Success Criteria:

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### Physics Talk 2.3

Newton’s Second Law

September 30, 2013HW:

• Do Now:

• Copy LO and SC

• Agenda:

• Do Now

• LO and SC

• Investigate

• Physics Talk, Notes

• Active Physics Plus

• Learning Objective:

• Students use F=ma to solve problems relating to Newton’s Second Law of Motion

• Success Criteria:

• Identify the forces acting on an object

• Determine when the forces on an object are either balanced or unbalanced

• Compare amounts of acceleration semi-quantitatively

• Apply Newton’s Second Law of Motion

• Apply the definition of the Newton as a unit of force

• Set up Notebook for tomorrow

September 28, 2010HW: Grade Report Signed, Missing work due Friday

• Do Now:

• Agenda:

• Do Now

• LO and SC

• Investigate

• Physics Talk, Notes

• Active Physics Plus

• Learning Objective:

• Students use F=ma to solve problems relating to Newton’s Second Law of Motion

• Success Criteria:

• Identify the forces acting on an object

• Determine when the forces on an object are either balanced or unbalanced

• Compare amounts of acceleration semi-quantitatively

• Apply Newton’s Second Law of Motion

• Apply the definition of the Newton as a unit of force

• #1-5 30 minutes

• 6-7 10 minutes

• Explain the relationship between Mass, Acceleration, and Force.

• Hint: keep mass constant, explain what happens to force and acceleration

• Hint: keep force constant, explain what happens to mass and acceleration

• Hint: given a constant acceleration, how are mass and force related?

• Vocab: Mass, Acceleration, Force, increase, decrease, constant

September 29, 2010HW: PTG 1-4, 6, 7, 9-11

• Do Now: How did the mass on the car change the force needed to push it?

• Agenda:

• Do Now

• LO/SC

• Physics Talk

• PTG

• L.O. Students use F=ma to solve problems relating to Newton’s Second Law of Motion

• S.C.

• Identify the forces acting on an object.

• Determine when the forces on an object are either balanced or unbalanced.

• Compare amounts of acceleration semi-quantitatively.

• Apply Newton’s Second Law of Motion.

• Apply the definition of the Newton as a unit of force

• Look at pg. 162

• Explain why force is measure in Newtons which is defined as

• 1N=1kg*m/s2

• What is Newton’s Second Law?

• Relationship between force, mass, and acceleration

• F=ma

• What is the equation for Newton’s Second Law?

• What does each variable represent?

a = acceleration (m/s2)

F = force (Newton – N)

m = mass (kg)

• What is a Newton?

• What causes acceleration?

• The Newton is the unit for force. 1 N is the force required to make on kg of mass accelerate at 1m/s2

• 1N = 1 kg*m/s2

• Unbalanced forces

• What are some examples of Newton’s second law?

• Does Newton’s 2nd Law ever stop working?

• If you push a small cart with a large force, it will accelerate a great deal. If you use the same force on a car, it will accelerate less.

• No, there is always acceleration, it just may be too small to measure.

• A tennis ball with mass 58g accelerates at 430m/s2 when it is served. What is the force responsible for this acceleration?

• Given:

• m =58 g = 0.058 kg

• a = 430m/s2

• Unknown: Force

• Tool: F = ma

• Solution:

• F = 0.058kg*430m/s2

• F = 24.95 kg*m/s2

• F ≈ 25N

• Could an identical force accelerate a 5.0 kg bowling ball at the same rate?

• Given:

• F=25N

• m = 5.0kg

• Unknown: acceleration

• Tool: F=ma

• Solution:

• 25N=5kg*a m/s2

• 25N/5kg = a

• Could an identical force accelerate a 5.0 kg bowling ball at the same rate?

• No, an identical force would not accelerate the bowling ball at the same rate.

• Solution:

• 25N=5kg*a m/s2

• 25N/5kg = a

• A tennis racket hit a sand-filled tennis ball with a force of 4 N. While the 275 g ball is in contact with the racket, what is its acceleration?

• Given:

• F=4N

• m=275g = 0.275 kg

• Unknown: acceleration

• Tool: F=ma

• Solution:

• 4N=0.275kg*a m/s2

• What is the acceleration due to gravity?

• What does this mean about the force of gravity?

• What is weight?

• 9.8 m/s2

• If you drop a 1kg mass, there is a force of 9.8N acting on the object

• The vertical, downward force exerted on a mass as a result of gravity

• How do you calculate an object’s weight?

• What do the variables mean?

w = weight

m = mass in kg

g = acceleration due to gravity (9.8 m/s2)

September 30, 2010HW: 2.3 PTG #1-4, 6, 7, 9-11, Due Friday

• Do Now: Use the concept of F=ma to explain why someone has different weights on different planets.

• Agenda:

• Do Now

• LO/SC

• Physics Talk

• Learning Objectives:

• Students use F=ma to solve problems relating to Newton’s Second Law of Motion

• Explain the difference between mass and weight

• Success Criteria:

• Identify the forces acting on an object

• Determine when the forces on an object are either balanced or unbalanced

• Compare amounts of acceleration semi-quantitatively

• Apply Newton’s Second Law of Motion

• Apply the definition of the Newton as a unit of force

• Describe weight as the force due to gravity on an object

• What is a free-body diagram?

• When will an object accelerate?

• A diagram showing the forces acting on an object

• Balanced force=no acceleration

• Unbalanced forces=acceleration

• Example of free body diagram for

• Example of a free-body diagram for a car moving on the road at a constant velocity.

• Is the car accelerating?

Since the car is traveling at a constant speed, it is not accelerating. This means that the force of the road on the tires is equal to the air resistance and we have balanced forces.

• In your notebook: Pg. 170