science 4.0 updated

Force 

Force 

In science, it is a push or a pull that acts on an object

contact force 

A contact force must touch the object that they push or pull, like a tennis racket hitting a tennis ball

Action-at-a-distance 

force that can push or pull an object without touching it

Gravity 

The attraction between two objects due to their mass

Mass

Mass is the amount of matter in an object 

Weight 

Weight is the amount of force an object has due to gravity 

The unit of force 

The metric unit of force is the newton (N), named after a man named Isaac Newton. Since weight is the force of gravity, it is measured in newtons. On Earth 1kg = 9.8N(weight).

Spring scale 

A device used to measure weight. It has a hook on the end and as more force is put on the scale, the hook streches, leading to an increase on the scale. 

Calc the force of Gravity (weight) 

Force of gravity = (mass of object) x (the strength of
earth's gravitational field (9.8N))

Friction 

The force that goes against an object in motion.

Work 

The amount of effort spent when a force causes an object to move a distance.

Work and Energy 

Energy is defined as the abilty to do work or the ability to apply a force and move an object. 

Kinetic Energy 

The energy an object has when it is moving.

Thermal energy 

The total amount of all the kinetic energy of all the particles in an object or substance. 

Potential Energy 

Any energy stored is called potential energy 

Gravitational potential energy

The potential energy of an object that is able to fall

Work produces a change in energy 

When looking at potential energy, a backpack at rest on the floor has no gravitational potential energy since it cannot fall. When you lift the backack, you are doing some sort of work since you are apply a force over a certain distance. 

Work done by friction 

Energy can not be created or destroyed. Energy can only be transfered from one object to another or transfomed from one form of energy to another. Thermal energy is the total energy of the moving particle in a substance. 

Calculating work 

(Work in joules) = (Force in newtons) x (distance in metres)

Machine 

Any mechanical system that reduces the force needed to accomplish work

How do machines make work easier

Machines make work easier in three ways:

-by increasing the force that can be
applied to an object

-by increasing the distance over which
the force is applied

-by changing the direction of a force

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Changing direction 

A machines that changes the direction of the force you apply. For examples the pully on the top of a flagpole is one example of this. When someone applies a downward force on the rope, and an upward force is exerted on the flag.

Input and outpure forces 

The force that is applied to a machine is called the input force. The force that the machine applied to the object is called the output force. 

Mechanical Advantage 

The amount by which a machine can multiply an input force. 

mechanical advantage= output force in newtons devided by input force.

Mechanical advantage of 1 

A machine has a the mechanical advantage of 1 if both the input and output force is the same size. Machines that have the mechanical advantage of 1 only change the direction between the input and the output forces. 

Ideal mechanical advantage 

In an actual machine the input force is converted to the thermal energy by the friction of the machine. Due to this the output force is less than the work done by the input force. An ideal machine has no friction, so no energy is converted into thermal energy. The MA of a machine that has a no friction is called the ideal mechanical advantage. Ideal mechanical advantage = input distance over output distance.

Ideal mechanical advantage of less than 1 

Sometimes the IMA is les than 1 and the output distance is greater. This usually mans that the speed at the ouptut is higher than the input. Examples are hockey sticks, baseball bats, and garden rakes. 

Inertia 

The tendecny of the objects in motion to stay in motion and objects that rest stay at rest, unless a certain force causes it to speed up or change direction.