What is Energy?, |What is a pulley and how does it work?,|what is opener work?

How did we use energy?

Boxes are carried,heavy furniture is shifted,and goods are transported over steep hills.People learned early in their existence how to simplify the works.They crouched down for lifting a box;mountain trails and mountain passes were made in widely curved serpentines;and pulleys were used in storage halls and harbours.Soon this knowledge was used in different ways.For example,a crown cap fits tightly on the bottle,and it is easy to open it with a bottle opener.

Why do mountain have serpentine roads?

If a work can do in different way.What matters is how it is done.For example,we can climb the mountain in two ways.If we take a shortest route,we need to apply a lot of force.If we gradually ascend towards the top using the serpentine roads,it takes long,but saves energy.it is based on the law of physics:Work=Force x Distance

Why is it difficult to move heavy furniture?

Heavy furniture exerts a high pressure force per unit area-downwards.If both the contact surfaces of the furniture and the surface of the floor are very rough,the surface adhere to each other.To move the furniture we have to overcome this force as static friction.It is smaller if the surfaces are smoother.When during the movement,it take converted into dynamic friction.It will be easier to transport heavy objects on wheels,and forces of friction always produce heat.In the stone age,human beings used this heat to make fire.

Why do we crouch down to lift a heavy box?

All of the body's centre of gravity normally lies near the belly button.When we bend forward and lift a heavy box,the centre of gravity of the'body plus the box' lies far away from our body.This puts a lot of pressure on the backbone,and the back muscles resist this.In contrast,when we crouch down and get up with the box,the centre of gravity remains near the body.This puts less pressure on the backbone and helps keep our backs healthy.

What is a pulley?

A pulley is a device to lift a heavy object in small force.It is made with a cable and a wheel of different sizes.Here the low again'Work=Force x Distance'is applicable as in the case of serpentines. Here 'distance'means the length of the cable.The wheels are wounded by the cable.The more the number of wheels,the smaller the force to be applied.we can find such pulleys on sailing ships for hoisting the sail.They are also used at construction sites to lift beams or other construction materials.Earlier,pulleys were used to put heavy ship boxes in storage spaces high above the ground.

How does a bottle opener work?

A bottle opener is a simple lever.It intensifies the force with which we remove the crown cap of a bottle.Levers are mostly rigid,rod-shaped objects that have a fulcrum at one place.The longer the arm of the lever,the lesser the force required to do the work.The law of physics'Work=Force*Distance'is applicable here too.The bottle opener is a one-sided lever.The longer the arm of the bottle opener,the easier it is to open it.Other examples of levers are pliers,scissors,crowbars,wrenches,paper punchers,and door handles.