Weight is what kind of force

All objects upon earth experience a force of gravity that is directed "downward" towards the center of the earth. The force of gravity on earth is always equal to the weight of the object as found by the equation:. F norm. The normal force is the support force exerted upon an object that is in contact with another stable object. For example, if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book. On occasions, a normal force is exerted horizontally between two objects that are in contact with each other.

For instance, if a person leans against a wall, the wall pushes horizontally on the person. Friction Force. F frict. The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it. There are at least two types of friction force - sliding and static friction. Thought it is not always the case, the friction force often opposes the motion of an object.

For example, if a book slides across the surface of a desk, then the desk exerts a friction force in the opposite direction of its motion. Friction results from the two surfaces being pressed together closely, causing intermolecular attractive forces between molecules of different surfaces.

As such, friction depends upon the nature of the two surfaces and upon the degree to which they are pressed together. The maximum amount of friction force that a surface can exert upon an object can be calculated using the formula below:. F air. The air resistance is a special type of frictional force that acts upon objects as they travel through the air. The force of air resistance is often observed to oppose the motion of an object.

This force will frequently be neglected due to its negligible magnitude and due to the fact that it is mathematically difficult to predict its value. It is most noticeable for objects that travel at high speeds e. F tens. The tension force is the force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting from opposite ends.

The tension force is directed along the length of the wire and pulls equally on the objects on the opposite ends of the wire. F spring. The spring force is the force exerted by a compressed or stretched spring upon any object that is attached to it.

An object that compresses or stretches a spring is always acted upon by a force that restores the object to its rest or equilibrium position. For most springs specifically, for those that are said to obey " Hooke's Law " , the magnitude of the force is directly proportional to the amount of stretch or compression of the spring.

Sanders' Site. Types of Forces Notes » Types of Forces. Forces A force is a push or pull acting upon an object as a result of its interaction with another object. My Resources. Classroom News. My Homework. Mass is never altered by location, the pull of gravity, speed or even the existence of other forces.

For example, a 2-kg object will have a mass of 2 kg whether it is located on Earth, the moon, or Jupiter; its mass will be 2 kg whether it is moving or not at least for purposes of our study ; and its mass will be 2 kg whether it is being pushed upon or not. On the other hand, the weight of an object measured in Newton will vary according to where in the universe the object is.

Weight depends upon which planet is exerting the force and the distance the object is from the planet. Weight, being equivalent to the force of gravity, is dependent upon the value of g - the gravitational field strength. On earth's surface g is 9. On the moon's surface, g is 1. Go to another planet, and there will be another g value.

Furthermore, the g value is inversely proportional to the distance from the center of the planet. So if we were to measure g at a distance of km above the earth's surface, then we would find the g value to be less than 9. The nature of the force of gravity will be discussed in more detail in a later unit of The Physics Classroom.

Always be cautious of the distinction between mass and weight. It is the source of much confusion for many students of physics.

As mentioned above , the friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it. For the purpose of our study of physics at The Physics Classroom, there are two types of friction force - static friction and sliding friction. Sliding friction results when an object slides across a surface. As an example, consider pushing a box across a floor. The floor surface offers resistance to the movement of the box.

We often say that the floor exerts a friction force upon the box. This is an example of a sliding friction force since it results from the sliding motion of the box. If a car slams on its brakes and skids to a stop without antilock brakes , there is a sliding friction force exerted upon the car tires by the roadway surface. This friction force is also a sliding friction force because the car is sliding across the road surface.

Sliding friction forces can be calculated from knowledge of the coefficient of friction and the normal force exerted upon the object by the surface it is sliding across. The formula is:. The coefficient value is dependent primarily upon the nature of the surfaces that are in contact with each other. For most surface combinations, the friction coefficients show little dependence upon other variables such as area of contact, temperature, etc.

The more that surface molecules tend to adhere to each other, the greater the coefficient values and the greater the friction force. Friction forces can also exist when the two surfaces are not sliding across each other. Such friction forces are referred to as static friction. Static friction results when the surfaces of two objects are at rest relative to one another and a force exists on one of the objects to set it into motion relative to the other object. Suppose you were to push with 5-Newton of force on a large box to move it across the floor.

The box might remain in place. A static friction force exists between the surfaces of the floor and the box to prevent the box from being set into motion. The static friction force balances the force that you exert on the box such that the stationary box remains at rest.

When exerting 5 Newton of applied force on the box, the static friction force has a magnitude of 5 Newton. Suppose that you were to push with 25 Newton of force on the large box and the box were to still remain in place. Static friction now has a magnitude of 25 Newton.

Then suppose that you were to increase the force to 26 Newton and the box finally budged from its resting position and was set into motion across the floor. The box-floor surfaces were able to provide up to 25 Newton of static friction force to match your applied force. Yet the two surfaces were not able to provide 26 Newton of static friction force. The nature of the gravitational force has been studied by scientists for many years and is still being investigated by theoretical physicists.

For an object the size of an airplane, the descriptions given three hundred years ago by Sir Isaac Newton work quite well. Newton developed his theory of gravitation when he was only 23 years old and published the theories with his laws of motion some years later.

The gravitational force between two objects depends on the mass of the objects and the inverse of the square of the distance between the objects.

Larger objects create greater forces and the farther apart the objects are the weaker the attraction. Newton was able to express the relationship in a single weight equation.

Weight is a force, and a force is a vector quantity having both a magnitude and a direction associated with it. For an airplane, weight is always directed towards the center of the earth.

The magnitude of this force depends on the mass of all of the parts of the airplane itself, plus the amount of fuel, plus any payload on board people, baggage, freight,