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

Chapter 10 Forces

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.

Chapter 10 Forces

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

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

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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?

Chapter 10 Forces

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