1. More One-Dimensional Kinematics
Unit 1 Presentation 4

2. Remember Our Kinematic Equations

3. Kinematics Example Problems
A car accelerates from rest to a speed of 10 m/s over 15 seconds. What was the acceleration of the car?

4. Another Kinematics Example Problem
Now find the distance it took the car in the previous problem to reach its final velocity of 10 m/s.

5. An Alternative Way to Solve the Same Problem

6. Free Fall
Free fall occurs when the initial velocity in the y-direction is equal to zero.
Think of simply dropping an object.
Lets look at the “big” kinematic equation and simplify it, solving for time:
Now, consider the only acceleration in the y-direction is the acceleration due to gravity (g) and the initial height is 0 meters:

7. More on Free Fall
Notice that the free fall equation is only dependent on height and the acceleration due to gravity.
NOT dependent on mass!
Hence, in the absence of air resistance and friction, any two objects dropped from the same height will impact the ground at exactly the same time.
Including a bowling ball and a feather!

8. Free Fall Example Problem
Calculate the time it takes for a ball to drop 10 meters.

9. Free Fall Example Problem
Calculate the time it takes for a ball to drop 100 meters.

10. Another Kinematics Example
A typical jetliner lands at a speed of 160 mi/hr and decelerates at a rate of (10 mi/hr)/sec. If the plane travels at a constant speed of 160 mi/hr for 1.0 sec after landing before applying the breaks, what is the total displacement of the aircraft between touchdown on the runway and coming to rest?
First, lets convert all of our units to the SI system:
Now find the displacement while the plane is coasting (no accel):

11. Another Kinematics Example Cntd.
Now, find the displacement while the plane is breaking:
Now, to find the total displacement, add the coasting and breaking displacements: