Gravity and Motion Galileos Story Gravity and Acceleration

Gravity and Motion

Galileo’s Story

Gravity and Acceleration • Objects fall to the ground at the same rate because the acceleration due to gravity is the same for all objects • What is acceleration? – The rate at which the velocity(speed) changes over time • All object accelerate towards the Earth at a rate of 9. 8 m/s per second. – Example: You drop a penny off the top of a building. It’s starting velocity is 0 m/s. After one second, the velocity has increased to 9. 8 m/s. After two seconds, the velocity is 19. 6 m/s.

Free Fall • Free Fall occurs when the only force acting on an object is gravity. • In Free Fall, the force of gravity is an unbalanced force, which causes the object to accelerate.

Video Time! Penny Drop! If a penny is dropped from a high enough building, can it seriously injure a person below?

Solving Problems with Free Fall y = 0. 5 gt 2 yy yy

Calculate height A stone is dropped down a well and it takes 1. 6 seconds to reach the bottom. The acceleration due to gravity is 9. 8 m/s 2 How deep is the well? You may assume the initial speed of the stone is zero. • G: g = 9. 8 m/s 2 t=1. 6 seconds • U: y • E: y = 0. 5 gt 2 • S: y = 0. 5 (9. 8 m/s 2) (1. 6)2 • S: 12. 54 meters

Your turn! Solve the problem below! A stone tumbles into a mineshaft and strikes bottom after falling 6. 1 seconds. How deep is the mineshaft? (Assume gravity = 9. 8 m/s 2) • G: • U: • E: y = 0. 5 gt 2 • S:

Solving for velocity: v = v 0 + gt How fast will a pebble be traveling 3 seconds after being dropped? Assume the initial velocity is 0 m/s and the acceleration of gravity is 9. 8 m/s 2. • G: g= 9. 8 m/s 2 t= 3 s vo= 0 m/s • U: v • E: v = v 0 + gt • S: v = 0 m/s + (9. 8 m/s 2)(3 s) • S: v= 29. 4 m/s

Your turn! Solve the Problem below! A penny dropped into a wishing well reaches the bottom in 2. 5 seconds. What was the velocity at impact? Assume the initial velocity is 0 m/s and the acceleration of gravity is 9. 8 m/s 2. • G: • U: • E: v = v 0 + gt • S:

Air Resistance and Mass • The acceleration due to gravity does not depend on the mass of the object which is falling. • However, we know that is not always the case. • RIGHT?

Air resistance • A type of fluid friction that acts on falling objects. • It is an upward force exerted on all objects. • Falling objects with greater surface area encounter more air resistance. • Which encounters more air resistance…crumpled paper or flat paper? • Which one falls faster?

Terminal Velocity • Air resistance increases as a falling object’s speed increases. • Eventually, the rate of acceleration is reduced to zero and the object falls with constant speed. • The maximum speed at which an object falls when limited by air resistance is called the terminal velocity.

It’s Raining Paper, Bananas, and Free Body Diagrams.

Projectile Motion • Projectile motion is the curved path an object follows when it is thrown or propelled near the surface of the Earth. • Projectile motion has two components – Horizontal motion – Vertical motion

Projectile Motion What do you need to consider when playing darts?

That’s a wrap for Forces!