newton’s 1st law of motion

Chapter 10 Forces

Objects will not begin to move or change motion until an unbalanced force acts on it.

Newton’s 1st Law of Motion

Inertia• All mass resists a change in motion

Depends on mass• Greater mass = more inertia

Chapter 10 Forces

Newton’s 2nd Law of MotionChanges in force & mass

• Acceleration increases • when force (push or pull) increases• when mass decreases

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Determining Acceleration• Acceleration (motion) depends on how much force is

used and the amount of mass.• acceleration = Force mass

Newton’s 2nd Law of Motion

Chapter 10 Forces

Newton’s 3rd Law of MotionIf one object exerts a force on another object, then the second object exerts a force back that is…equal in strength and opposite in direction on the first object.

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Momentum“quantity of motion” depends on the mass and the velocity

Momentum (p) = mass (kg) x velocity (m/s)

Chapter 10 Forces-

Conservation of MomentumMomentum is conserved..• when 2 objects collide• remains the same before and after the collision

Chapter 10 Forces

Pg.392 Calculating Force

A speedboat pulls a 55-kg water-skier. The skier to accelerates at 2.0 m/s2. Calculate the net force that causes this acceleration.

What is the question asking for?

What information have you been given?Mass of the water-skier (m) = 55 kgAcceleration of the water-skier (a) = 2.0 m/s2

Chapter 10 Forces

Pg.392 Calculating ForcePractice Problem

What is the net force on a 1,000-kg object accelerating at 3 m/s2?

F = ma =1,000 kg x 3 m/s2= 3,000 N

Chapter 10 Forces

Calculating MomentumWhich has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s, or a 4.0-kg sledgehammer swung at 0.9 m/s?

Read and Understand

What information are you given? Mass of smaller sledgehammer = 3.0 kg Velocity of smaller sledgehammer = 1.5 m/s Mass of larger sledgehammer = 4.0 kg Velocity of larger sledgehammer = 0.9 m/s

Chapter 10 Forces

Calculating MomentumWhich has more momentum: a 3.0-kg sledgehammer swung at 1.5 m/s or a 4.0-kg sledgehammer swung at 0.9 m/s?

What formula contains the given quantities and the unknown quantity?

Momentum = Mass x Velocity p = mv

Smaller sledgehammer = 3.0 km x 1.5 m/s = 4.5 kg•m/sLarger sledgehammer = 4.0 km x 0.9 m/s = 3.6 kg•m/s

Chapter 10 Forces

Calculating MomentumPractice Problem

A golf ball travels at 16 m/s, while a baseball moves at 7 m/s. The mass of the golf ball is 0.045 kg and the mass of the baseball is 0.14 kg. Which has greater momentum?

Golf ball: 0.045 kg x 16 m/s = 0.72 kg•m/sBaseball: 0.14 kg x 7 m/s = 0.98 kg•m/sThe baseball has greater momentum.

Chapter 10 Forces

Calculating MomentumPractice Problem

What is the momentum of a bird with a mass of 0.018 kg flying at 15 m/s?

0.27 kg•m/s (0.018 kg x 15 m/s = 0.27 kg•m/s)

Chapter 10 Forces

Section 5:Rockets and Satellites

How does a rocket lift off the ground?What keeps a satellite in orbit?

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What Is a Satellite?A projectile follows a curved path. The horizontal and vertical motions act independently.

Chapter 10 Forces

What Is a Satellite?The faster a projectile is thrown, the father it travels before it hits the ground. A projectile with enough velocity moves in a circular orbit.

Chapter 10 Forces

What Is a Satellite?Depending on their uses, artificial satellites orbit at different heights.

Chapter 10 Forces

End of Section:Rockets and Satellites