- Review velocity, acceleration and the conditions needed to cause acceleration - Observe and plot the change in acceleration of a rolling object with steepness - Learn to calculate final speed from average speed and acceleration TODAY’S OUTCOMES: FORCE, MOTION AND ENERGY

The mass in the level is in the fluid, NOT the bubble; the bubble shifts in the opposite direction of the fluid mass. The bubble points in the direction of the acceleration, opposite to the side on which you feel a force on your body. *Suppose we were on a bus, and had a carpenter’s level which we put on a level spot on the floor. What would be bubble do >when the bus starts moving? >when the bus is traveling down Euclid Avenue at constant speed? >when the bus stops? >when the bus makes a right turn? acceleration direction fluid left behind due to inertia bubble shift The bubble would shift to the front. The bubble would be centered, since there is no acceleration. The bubble would shift toward the right. The bubble would shift to the rear.

*If you were to move the level along the track you made for the rolling ball, taking the same path as the ball and going the same speed, where would the bubble be centered and where not? When the bubble was off-center, which direction would it be pointing? Explain by drawing a diagram showing the track and the bubble level. Diagrams will vary, but the bubble will shift toward the inside of the turn. Recall the example of a car making a sharp turn on a banked curve Which direction is the acceleration? Which direction does the driver “feel” like he is being “pulled” toward in the car? Toward the inside of the turn acceleration Is there really a force pulling the driver outward? What direction is the force really pointing, and why? The driver feels like he is “pulled” to the outside No - the force of the banked road pushes the car to the inside of the turn - the driver feels his body tending toward a straight direction due to the Law of Inertia, and the moving car pulls him inward.

Will you have problems pouring water into a glass when the train is sitting still? THOUGHT EXAMPLE #1: INERTIA AND ACCELERATION when the train is rolling at a constant speed of 100 mph? No when the train is speeding up? No - as long as the speed is constant, the water should pour into the glass just as it does when the train is still. (The train, passenger, pitcher, water and glass are all moving at the same velocity together!) when the train is braking? Yes - the water in mid-air will not accelerate with the train because there is no force on it - it will splash toward the rear. Yes - the water will keep moving forward as the train brakes.

A 100 lb. person is standing on a bathroom scale aboard a rocket ship. The rocket ship is moving upward at a constant speed of 100 mph. How will the measured weight compare to that of the weight measured on the ground? THOUGHT EXAMPLE #2: INERTIA AND ACCELERATION bathroom scale Under what conditions will the weight on the scale change? The weight will be the same! All forces are still balanced just as they are on the ground. Only if/when there is an change in the speed (acceleration) will the scale weight increase or decrease. ) Does the person’s mass ever change? No!

Are the forces on the ball all equal? You saw the ball did NOT keep the same speed - it accelerated. Last Lab - An accelerating ball No - because the ball is changing velocity, the forces on the ball are not equal - there is an external force.

- Velocity is both the speed and direction of an object or body - Any change in velocity is called an acceleration - Acceleration only occurs when forces on an object are not balanced WHAT YOU ARE EXPECTED TO KNOW:

- Review velocity, acceleration and the conditions needed to cause acceleration ✓ - Observe and plot the change in acceleration of a rolling object with steepness - Learn to calculate final speed from average speed and acceleration TODAY’S OUTCOMES: FORCE, MOTION AND ENERGY