# Forces

## Forces

A push or a pull can be a force. A force that acts on a body appears to alter the body ‘s velocity or direction.

• Newton (N) is the SI unit of force. It’s a number of vectors.
• We should suppress/add abilities. (More on force supplementation)
• We exert a Force while we force, drag, raise, bend, curl, break, stretch or grab.

## What can a force do?

• Render a body going stagnant
• Change a body’s pace
• Adjust the direction of the body’s motion (the direction of the body’s movement cannot be changed without changes in speed).
• Alteration of the body size or composition

## Gravitational Force

• A gravitational influence that depends only on the masses of the objects.
• Long-distance body operating at a distance
• Normally it can be ignored without a very big mass.

## Measures Electromagnetic

• It occurs between electric charges moving or stationary
• Can be an enticing or abhorrent Force

## Strong Nuclear Forces

Strengths of protons and neutrons and other sub-nuclear particles

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Keeps the atomic nucleus together because, through their reciprocal electric repulsion, they retain the protons together

## Weak Force:

• Responsible for encounters with radioactive decay and neutrino
• Quite poor and short-range
• Certain Control Styles

## Contact Force

Contact force is a force perpendicular to the surface experienced by a body when it is in physical contact with something else.

This happens when atoms of one object get too close to the atoms of another object. The contact forces are actually manifestations(signs) of the electromagnetic force.

Example: When you press your hand against your desk, you feel the repulsion of the electrons in the atoms of your hand against the electrons in the atoms of the desk.

## Frictional Force

Acts in the opposite direction to the direction of motion of the body

Resistive force acting between bodies that tends to oppose motion

For moving objects,

Contact force now consists of Normal contact force (N) and Frictional force (f)

Contact force is the resultant of N and f

## Viscous Force (Drag Force)

• When a solid move in a fluid, it will experience resistance to its motion

• Dependent on the speed of the object

• For objects moving at low speeds, viscous force is proportional to its speed

• For objects at high speeds, the viscous force is proportional to the square of the speed of the car

• Depends on the fluid involved

• Higher viscosity in denser fluids

• Dependent on the nature of the fluid

## Tension force • Bi-directional force
• Always directed away from the objects and along the length of the string
• More on Contact Force

As shown in the image above, the impact force (or natural force) of an object lying on a table is active upwards.

Note the remainder of the case. With the First Law of Motion of Newton, you will know that the net resulting force on the object is negative (i.e. that all forces are equally balanced). You will know this law in following sub-topics. Therefore, the usual force and weight are the same (acting in the same direction).

The regular force begins at the base of the box, where the box and the table are in touch.

Weight stops at the middle of the box mass (indicated by C.M.C.M.).

## Turning Effect of Force:

If a body will spin around an axis under the operation of a net external force, it appears to turn in the direction of the applied force.

## Examples of turning effect of force:

• The swing would revolve around its hinge if a human moves a swing.
• A worker uses a power to move a nut.
• An individual takes out the cork of a bottle by pressing the opener’s lever forward.
• A door knob has a power and the door is opening around the hinge.
• By using force on the bottom, a driver will turn a steering wheel.

## Movement of Force:

The moment of a force or torque is defined by r as the turning effect of the strength around a pivot, the consequence of force (F) and the distance between the force and the pivot perpendicular to the force.

Newton meter (Nm) is the SI moment unit of a power. It’s an number of vectors.

The grip rule perpendicularly to the force plane and pivot point is given in its direction, which is parallel to the rotation axis.

r=F×dr=F×d

where
r is the moment of force/torque
F is the force
d is the perpendicular distance from the line of action of the force to the pivot

## Couple A couple is a pair of forces, equal in magnitude but opposite in direction, whose lines of motion do not coincide.

Will still rotate as there is a net moment

As forces are equal and opposite, resultant force is zero and so there is no linear acceleration

r=F×dr=F×d

Torque (Moment of a couple) is the product of one of the forces and the perpendicular distance between their lines of action of the forces.

## Newton’s First Law of Motion We mean that if two or more external forces acting on the organism do not produce a net effect, i.e. a vector sum of forces is zero. The resulting loss of strength would not generate a net acceleration and therefore, the body can rest or travel straight at its original constant speed.

# This is Newton’s First Law of Motion

• An external force is one which has its origins outside the body. e.g. body weight and rubbish
• The resulting intensity is the vector total of all external forces on a body.
• Newton’s First Rule of Motion: the rule of inertia is also established. Inertia is a mass resistance property against any change in its initial state of rest or activity. The larger the mass of a muscle, the greater its inertia and its resistance to changes in rest or movement.
• A rest body means that the corresponding net force is zero.
• There are, however, no powers acting on the body, not necessarily.

For example, the resulting force of a box sitting on a table is zero. However, on the box, there are two powers! One force is the weight of the box, and the other force is the natural force.

The standard weight and force arrows have the same size but opposite length (same magnitude). Normal force (or reaction force) is an external force exerted perpendicularly by the surface in reaction to anybody placed against it. The normal force arrow starts from the base of the box (contact between the box and the table top).

The weight arrow starts from the center of mass of the box (labelled as C.M.), as indicated by the black dot.

Other Laws of motion

Newton’s 3 laws of motion are:

1st law: The first law of Newton ‘s movement states that, until an actual consequent force operates on the body, it shall proceed in its rest or uniform movement in straight line.

2nd Law: The Second Law of Newton states that the quantities of a body’s momentum shift are relative and movement is oriented towards the body.

Third law: the third law of Newtons states: if body A exercises a power on body B, body B exercises a force of the same scale, but on body A the reverse.

In the following articles, we will research the second rule of motion more closely.

## Newton’s Third Law of Motion Newton’s third law states that: If body A exerts a force on body B, then body B exerts a force of equal magnitude but in the opposite direction on body A.

Forces always occur in pairs – Action force and reaction force.

Action and Reaction Forces

Some properties of the action and reaction forces are as follows:

The action and reaction forces are equal in magnitude.

The action and reaction forces act opposite to one another.

The action and reaction forces act on different bodies.

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