1. Kinetic Energy Conner Middle School 8 th Grade Science

2. KINETIC ENERGY VIDEO https://www.schooltube.com/video/faddf7cb14ade293baad/

3. Gravity  The force of attraction between any two objects that contain mass. i.e. You have mass, and so does Earth.

4. Gravity  ________________________________________ ____________________. i.e. You have mass, and so does Earth.

5. Gravity  Here on Earth, gravity pulls on EVERYTHING at the same acceleration of 9.8 m/s 2.  So which will hit the ground first, the medicine ball or the basketball?

6. Gravity  Here on Earth, gravity pulls on __________ at the _________________________.  So which will hit the ground first, the medicine ball or the basketball?

7. Pendulum Lab Let’s look back at our lab from yesterday…  We had three different weights, but should have had relatively similar number of swings. Right?  That’s because gravity is acting on all three weights EXACTLY the same. As long as the angle of drop, length of string, time, etc. are all constant or controlled.  However, which weight contained more ENERGY (kinetic energy)?

8. Kinetic Energy Energy is defined as the ability to do work. When the work is actually being done, we term the energy “kinetic.” Kinetic energy is the energy of motion. For example, a rubber band zinged from your finger has kinetic energy.

9. Kinetic Energy ______________________________ When the work is actually being done, we term the energy “kinetic.” __________________________________. For example, a rubber band zinged from your finger has kinetic energy.

10. KINETIC ENERGY For moving objects, we can easily calculate kinetic energy using the formula: KE = ½ mv 2 Kinetic energy is directly proportional to the mass of the object and to the square of its velocity: K.E. = 1/2 m v 2. If the mass has units of kilograms and the velocity of meters per second, the kinetic energy has units of Joules (m 2 v/s).

11. KINETIC ENERGY For moving objects, we can easily calculate kinetic energy using the formula: _________________ Kinetic energy is directly proportional to the mass of the object and to the square of its velocity: __________If the mass has units of kilograms and the velocity of meters per second, the kinetic energy has units of ___________(m 2 v/s).

14. Sample Problem What is the kinetic energy of a 45 kg object moving at 13 m/sec? Step 1 First we identify the information we are given in the problem: mass = 45 kg velocity = 13 m/sec Step 2 Next, we place this information into the kinetic energy formula: KE = ½ mv 2 KE = ½ (45 kg)(13 m/sec) 2 Step 3 Solving the equation gives a kinetic energy value of 3802.5 J. Note: The unit for energy is the same as for work: the Joule (J).

15. Sample Problem What is the kinetic energy of a 45 kg object moving at 13 m/sec? Step 1Step 2Step 3 Note:

16. A 55 kg man runs at a speed of 4 m/s. Find his kinetic energy. Step 1: In this problem we are given the following: m = 55 kg v = 4 m/s Step 2: Plug the data into the given formula: KE = ½ mv 2

17. A 55 kg man runs at a speed of 4 m/s. Find his kinetic energy. Step 1: In this problem we are given the following: m = 55 kg v = 4 m/s Step 2: Plug the data into the given formula: KE = ½ mv 2

18. KINETIC ENERGY PROBLEMS  What is the kinetic energy of a bicycle with a mass of 14 kg traveling at a velocity of 3.0 m/s?  If a bowling ball has a mass of 10 kg and is rolled with a velocity of 15 m/s, what is the ball’s kinetic energy?  A 1200 kg automobile is traveling at a velocity of 100 m/s. How much kinetic energy does it possess?