IB Physics 11 Mr. Jean September 13 th, 2013

The plan: Video clip of the day HW Check Free Fall Motion Gravity’s acceleration

Free Falling Objects: When an object is dropped. –1) There is NO account for air resistance. –2) All Free-Fall objects fall at the same rate –What happens when there is no gravity?

Gravity: An object is at rest and is dropped 1 meter. The acceleration of gravity is -9.8m/s 2. How long does it take to hit the ground? HINT: x f - x i = v i t + ½ (a)(t 2 )

Gravity: Sarah is an excellent soccer player and hasn’t told anyone. Her best move is to kick the soccer ball straight up in the air to delay the game. The soccer ball leaves her foot from the ground with a velocity of 20m/s (upwards). How long does it take for the ball to hit the ground?

Gravity: Free fall Sarah is an excellent soccer player and hasn’t told anyone. Her best move is to kick the soccer ball straight up in the air to delay the game. The soccer ball leaves her foot from the ground with a velocity of 20m/s (upwards).

Gravity: Free fall Sarah is an excellent soccer player and hasn’t told anyone. Her best move is to kick the soccer ball straight up in the air to delay the game. The soccer ball leaves her foot from the ground with a velocity of 20m/s (upwards).

Gravity: Free fall Sarah is an excellent soccer player and hasn’t told anyone. Her best move is to kick the soccer ball straight up in the air to delay the game. The soccer ball leaves her foot from the ground with a velocity of 20m/s (upwards).

Gravity: Sarah is an excellent soccer player and hasn’t told anyone. Her best move is to kick the soccer ball straight up in the air to delay the game. The soccer ball leaves her foot from the ground with a velocity of 20m/s (upwards). How long does it take for the ball to hit the ground?

Acceleration of Gravity on Earth: a = ∆v = -9.81m/s ∆t 1s

How gravity is calculated on Earth and other planets: g = acceleration due to gravity (m/s²) G = universal gravitational constant (m³/kg/s²) M = mass of the body (kg) r = radius of the planetary body (m)

Constant acceleration model with unknown acceleration: x f - x i = ½ (v i + v f ) t x f = Final distance (m) x i = Initial distance (m) v f = Final velocity (m/s) v i = Initial velocity (m/s) t = time (s)

Strobe Light Demonstration: If I use a strobe light in class is this going to be a problem for anyone?

Strobe Light Demonstration: Key points: –Falling droplets of water over a constant time frame. –Each drop with a different degree of separation from the previous. –The pattern of drops SHOULD (haha) resemble the image on the left.

Time (s)Velocity (m/s)

Problems: A ball is dropped from the top of CN tower which is 440m above ground. The acceleration of gravity is -9.81m/s 2. How long does it take for the ball to hit the ground? A golf ball is hit straight up with the initial velocity of 50m/s. This action takes place on the moon. The moon’s gravity is -3.4m/s 2. How long does it take for the ball to hit the surface of the moon?

A ball is dropped from the top of CN tower which is 440m above ground. The acceleration of gravity is -9.81m/s 2. –A) How long does it take for the ball to hit the ground? –B) At what velocity does it hit the ground?

A) How long does it take for the ball to hit the ground?

B) At what velocity does it hit the ground?

A golf ball is hit straight up with the initial velocity of 50m/s. This action takes place on the moon. The moon’s gravity is -3.4m/s 2. A) How long does it take for the ball to hit the ground if the maximum height is 357.2m? B) How fast does it hit the ground?

For this weekend: Pages 25 to 45 Formula Sheet handed out on Monday Expect an assessment between September 20 – 27 th. (some day between)

B) How fast does it hit the ground?