#### 5 Oct 2009 jwp9447»(Apprentice)

Physics: The First Step of Robotics-1(Mechanical Energy)

Physics: The First Step of Robotics-1(Mechanical Energy)

As you know, physics is the most important thing we have to know to do robotics. So first, lets talk about ‘mechanical energy’.

Kinetic Energy:
This is a energy that occurs when a object moves.
It’s mathematical formula is E=1/2mv2. ‘M’ stands for mass, and ‘V’stands for velocity or speed. It mearsured in Joules or ‘J’, maded after the physicist “Joules”.

(Examples: A running man, trains, buses, cars, planes, rockets)

Potential Energy:
This energy occurs due to the height of an object. If I am in high above
Mt. Everest, that means I have potential energy. It’s mathematical formula is E=9.8mh. ‘M’ stands for mass, and ‘h’ stands for height. It mearsured in Joules or ‘J’, maded after the physicist “Joules”.

(Example: In above a building, tower, mountain, inside a flying plane)

Mechanical Energy:
This energy is measured in ‘kinetic energy+potential energy’ or
‘1/2mv2+9.8mh’. Mechanical energy is very useful in our lives. Let solve this question.
—A ball is about to fall down and collide with the ground. The ball fell down at the height of 100 meters. Calculate the velocity or speed of the ball when it collides with the ground.
A: First we don’t know the mass of the ball. So lets just skip that one.
When the ball fell at the height of a 100m, the kinetic energy is 0J because it didn’t move, and the potential energy is 9.8*100 so its 980J. So the mechanical energy at this point is 980J+0J so its 980J!

But when the ball fell, the potential energy gets smaller because the height is getting low. While since the ball is gaining speed, it gains more kinetic energy! So at any point of the route where the ball is falling, the mechanical energy is 980J!

When the ball collides with the earth, we already knowe that the mechanical energy is 980J. And since the height is 0 meters, the potential energy is oJ. So this means 1/2v2+9.8h=980, the potential energy is 0J, so
1/2v2=980.