Kinetic Energy Conner Middle School 8th Grade Science

KINETIC ENERGY VIDEO

https://www.schooltube.com/video/faddf7cb14ade293baad/

Gravity

The force of attraction between any two objects that contain mass.

i.e. You have mass, and so

does Earth.

Gravity

Here on Earth, gravity pulls on EVERYTHING at the same acceleration of 9.8 m/s2.

So which will hit the ground first, the medicine ball or the basketball?

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)?

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.

KINETIC ENERGY

For moving objects, we can easily calculate kinetic energy using the formula:

KE = ½ mv2

Kinetic energy is directly proportional to the mass of the object and to the square of its velocity: K.E. = 1/2 m v2. If the mass has units of kilograms and the velocity of meters per second, the kinetic energy has units of Joules (m2v/s).

Sample ProblemWhat 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 mv2

• • 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).

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 kgv = 4 m/s

Step 2:

Plug the data into the given formula:

KE = ½ mv2

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?