Embedded Files
Chapter 3: Lesson 3 - Acceleration due to Gravity
Chapter 3: Lesson 3 - Acceleration due to Gravity
Mini-Lab Demonstration #1:
Mini-Lab Demonstration #1:
Lets look at the acceleration of a golf ball down a ramp. Is it uniform?
We will measure the time it takes the ball to travel 0.4 m and then predict how long it will take for the ball to go 0.8 m.
Watch the video to see the demonstration.
Was your prediction correct?
Free Fall:
Free Fall:
An object is in free fall when there is little or no air resistance and gravity is the only force affecting a falling object.
Elapsed time is the time that has passed since the beginning of the fall.
This picture shows a girl dropping a ball off the side of the cliff. We can tell that the ball is speeding up because the spacing between the black dots is increasing.
If we were to add velocities to the previous picture, then we would see that the velocity of the ball increases by 10 m/s every single second.
Something is speeding up the ball as it moves towards the Earth. That something is the acceleration due to gravity. Acceleration due to gravity is really long to say and physicists are lazy, so they just abbreviate it and say gravity. Even though we don't normally say the "acceleration due to" part, do not forget that gravity is an acceleration!
Gravity is abbreviate with a 'g' and the number that we will use for the gravitational accleleration here on Earth is g=9.8 m/s2.
Check Your Understanding:
Check Your Understanding:
For the two questions below, think about the question, then click on the down arrow when you have your answer to check to see if you are correct. Use the picture to help you.
Joe throws a ball into the air with an initial vertical velocity of 40 m/s. As the ball moves up, the vertical velocity of the ball decreases.
What is the vertical velocity of the ball at the top of the parabala?
The vertical velocity is 0 m/s. The ball has to stop before it changes direction to come back down.
2. What is the acceleration at the top of the parabola?
Most people want to say 0 m/s2 because the ball's velocity is 0 m/s. DO NOT THINK THAT!! What is pulling on the ball? Gravity! Gravity is 9.8 m/s2 all throughout the ball's trip through the air. The acceleration of the ball is 9.8 m/s2 going up, 9.8 m/s2 going down, and 9.8 m/s2 at the top of the parabola. In this situation, the acceleration of the ball will always be 9.8 m/s2.
Mini-Lab Demonstration #2:
Mini-Lab Demonstration #2:
Lets go back to our golf balls and the ramp. I will release golf ball #1 at the 40 cm mark and golf ball #2 from the 80 cm mark at the same time.
Do you think that the golf balls will get closer together, farther apart, or stay the same distance apart when they reach the floor and travel down the hallway?
What happens to the distance between the golf balls?
What does this tell you about the acceleration of each golf ball?
The acceleration of the golf balls are the same. Golf ball #1 had a larger distance to accelerate before it reached the floor, so when it reached the floor, it had a larger velocity than golf ball #2, which only had a small distance in which to pick up speed.
Now I will release golf ball #1 from the top and when that golf ball reaches the 40 cm mark, I will release golf ball #2. Do you think the golf balls will get closer together, farther apart, or stay the same distance apart when they reach the floor and travel down the hallway?
What happens to the distance between the golf balls?
What does this tell you about the acceleration of each golf ball?
The acceleration of the golf balls are the same. Each had the same distance to accelerate and each golf ball had the same velocity when it reached the floor.
Bowling Ball vs Feather:
Bowling Ball vs Feather:
What do you think will happen if we dropped a bowling ball and a feather on Earth when there is no air resistance? Click on this video to see!
Did the bowling ball and the father react how you thought?
(This is one of my favorite videos to show! I love watching this! I also think that dramatic music is kinda funny.) :)
You have finished Lesson 3!
You have finished Lesson 3!
Be sure to head over to google classroom and fill out the exit pass.
Report abuse