Forest PHYS100 Demos Week3

Parabolic Motion:

For this demonstration I will ask the students what path they think any projectile will take. Bryce will put a projection of a parabola up on the board and we will throw a ball back and forth to each other. The trajectory of the ball will follow the parabola and we will investigate the height kinematic equation to see why this is. I will then ask them if I have a ball thrown straight up into the air, what will the position, velocity, and acceleration vs. time graphs look like. I will show this using the kinematic equations because the position function is a parabola, the velocity function is a line, and gravity is constant.

Ball Drop and Shoot:

For this demonstration I will ask the students which will hit the ground first: an object that is dropped, or an object that is shot horizontally. For every answer that the students provide I will ask them for reasons as to why they believe so. After a sufficient amount of guesses have been made, then I will show that both balls hit the ground at the same time. The mathematical proof for this is very simple. I will ask the students for the equations for the height of the ball that is being dropped and the ball that is being shot. Since the ball that is being shot has no initial y component to its velocity, the equations will be the same. This will yield the same time of flight for both balls. I will then explain that the x and y components of projectile motion are completely independent for these simple cases.

Monkey Shoot:

For this demonstration I will ask the class where I should aim my dart gun in order to hit the monkey before it hits the ground. You can either shoot slightly above the monkey, slightly below the monkey, or directly at the monkey. For any answer the students give I will ask them for justification as to why they think so. Then I will aim directly at the monkey and observe what happens. The projectile will hit the monkey while it is falling. The main reason is that both the bullet and the monkey have the same downward acceleration. I can also give a mathematical proof using the kinematic equations.

Ball in a Cart: Relative Motion For this demonstration I will use the PASCO track with a spring launcher and a ball placed on top of a cart. I will ask the students what will happen if the ball is fired up while the cart moves horizontally at a constant velocity. Any answer will require an explanation as to why they believe their answer. With a constant horizontal velocity, the ball will be fired into the air and it will fall back into the cup. I will then ask the students what would happen if the cart were accelerating and ask them to provide an explanation as to why the ball would not be caught in the cup.

Forest_PHYS100_Demos