Skydiving from space http www youtube comwatch v

Skydiving from space!! http: //www. youtube. com/watch? v= FHtv. DA 0 W 34 I ¡ What can potentially go wrong? ¡ Does his acceleration change? ¡

Review: Newton’s 1 st Law of Motion is inertia: “Every object continues in its state of rest, or a uniform speed in a straight line, unless acted on by a nonzero force. ”

Newton’s 2 nd Law of Motion states: acceleration = force/mass

Homework Review Questions?

Review What is the net force on the box? Magnitude = 5 N Direction = 3 N 2 N

Review What is the net force on the box? Magnitude = 4 N Direction = 4 N 5 N 5 N

Quiz Review What is the acceleration? a= F m 2 kg a = 4 N / 2 kg 4 N a = 2 m/s 2

Review The force of gravity between the moon and an object near its surface is much smaller than the force of gravity on the Earth. A bowling ball with a mass of 7. 51 kg is pulled downward with a force of 12. 2 N. What is the acceleration of the falling bowling ball on the moon? m = 7. 51 kg F = 12. 2 N a = 12. 2 N / 7. 51 kg = 1. 6 m/s 2

Newton’s Laws of Motion What is Freefall? Freefall is when the force of gravity is the only force on an object.

Free Fall Free fall really only occurs in a vacuum or in space where there is no air. If we drop a rock and a feather off in a vacuum, which will hit the ground first?

Free Fall If we drop a rock and a feather off in a vacuum, which will hit the ground first? Galileo said they would hit the ground at the same time, but why? m = 1 kg, F =10 N m =. 01 kg, F =. 1 N a = F/m a = 10 N/1 kg a =. 1 N/. 01 kg a = 10 m/s 2

Non-Free Fall Acceleration Most often, we have to consider airresistance for falling objects. Air resistance, which is a force of friction, depends on two things: 1. Surface Area 2. Speed

Non-Free Fall Acceleration Net Force = Weight – Air Resistance As a skydiver falls faster and faster, the acceleration decreases because the air resistance increases as the speed increases.

Non-Free Fall Acceleration Net Force = Weight – Air Resistance When the air resistance increases enough, the net force becomes 0 and acceleration stops. Does this mean the skydiver stops? No! It means the skydiver is no longer gaining speed – this speed is the terminal velocity.

Non-Free Fall Problems Mass = 85 kg Diagram A Force = 833 N Mass = 85 kg Acceleration = 833 N/85 kg = 9. 8 m/s 2

Non-Free Fall Problems Mass = 85 kg Diagram B Force = 833 N – 350 N = 483 N Mass = 85 kg Acceleration = 483 N/85 kg = 5. 7 m/s 2

Non-Free Fall Problems Mass = 85 kg Diagram C Force = 833 N – 700 N = 133 N Mass = 85 kg Acceleration = 133 N/85 kg = 1. 6 m/s 2

Non-Free Fall Problems Mass = 85 kg Diagram D Force = 833 N – 833 N = 0 N Mass = 85 kg Acceleration = 0 N/85 kg = 0 m/s 2

How are you feeling about this concept? ¡ Reflection How well do you understand Newton’s 1 st Law? How about his 2 nd Law? How about What can you do to improve your understanding?