Mass, Motion, Force and Work

Transcription

1 Mass, Motion, Force and Work Mass Motion Force Work

2 Mass Mass Volume Density

3 Mass Specific Volume Specific Gravity Flow Rate

4 Mass Mass is a measurement of a substance that quantifies its resistance to changes in its movement. Or you could say the mass of an object is gauged by measuring the force needed to move the object. The resistance an object has to change in movement is called inertia. An object with a large mass has a large inertia.

5 Mass An object with a small mass has a small inertia. The mass of an object, not its size determines its inertia. The mass of object can also be measured by the force it creates when placed in a gravitational field. This force is called the object s weight.

6 Volume The volume of a substance is the amount of three dimensional space it occupies. As the volume increases, the space it occupies also increases. Volume is expressed in three dimensions, length, width, and height. Therefore the units are cubed.

7 Density Density combines the characteristics of mass and volume in a way that indicates the compactness of a substance. The density indicates the amount of mass (inertia) present in each unit of volume occupied by an object. The density of a substance is equal to its mass divided by its volume. Lbm/ft3

8 Specific Volume The specific volume of a substance describes the amount of volume occupied by one unit of the object s mass. Specific volume is the inverse relationship of density so it is equal to its reciprocal. The greater an object s specific volume, the smaller the mass contained in a unit of its volume.

9 Specific Gravity The specific gravity of a substance is the ratio of its density to that of a substance at standard conditions. In cases of liquid pure water is used at 60 F where it has a density of 62.4 lbm/ft3 In cases of gases standard air is used at 60 F with a pressure of psiahas a density of lbm/ft3

10 Flow Rate A rate is a measure with respect to a unit change in time. Velocity is a an example of a rate measurement. Velocity measures the rate of distance change occurring as an object travels per unit of time. Mass flow rate measures how much mass is moving per unit of time. Volume flow rate measures how much volume is moving per unit of time.

11 Motion Motion Speed Velocity Momentum Acceleration Acceleration of Gravity

12 Motion All interactions between matter are described by Sir Isaac Newton s three laws of motion. Newton s first law of motion states that an object at rest in a uniform linear motion will remain in its present condition, unless acted upon by a force. Newton s second law of motion states that an unbalanced force acting upon an object will produce an acceleration in the direction of the applied force.

13 Motion Newton s third law of motion states that a force acting on an object creates a opposing force that is equal in strength but having a direction that opposes the applied force. This relationship is related to a characteristic of moving objects called momentum.

14 Speed The simplest form of motion is represented by an object that is moving at a constant speed in a straight line. The average speed of motion is equal to the distance an object moves divided by the length of time the object is in motion.

15 Velocity Velocity is the distance that an object travels in a specified direction within one unit of time. Velocity and speed are very similar, only speed does not indicate direction of movement. Therefore two variables are required to properly describe an objects velocity, speed and direction. If either speed or direction is changing then the velocity of the object is changing.

16 Momentum Momentum is a property of moving objects. It is equal to an object s mass multiplied by its velocity. Based on this relationship, it takes more force to stop a heavy object than it does a light object. Newton s laws are based on a general conservation law which states that in any interaction between two or more objects, momentum must be conserved.

17 Acceleration Acceleration is the time rate of change of an object s velocity. Objects in motion frequently experience changes in their velocity and momentum as external forces produce changes in speed or direction. Motion in which the velocity is changing is known as accelerated motion.

18 Acceleration of Gravity The simplest form of accelerated motion is an object experiencing free fall, as its velocity changes at a constant rate. The acceleration rate of gravity on an object is at a constant rate of 32.2 feet per second. The effect of earth s gravity on an object diminishes as the distance between the object and the center of earth increases.

19 Force Force Weight Pressure Atmospheric Pressure

20 Force A force is any action that distorts matter or generates changes in the motion of an object. When a force is applied to a substance or object, it can produce one to five reactions. A force can cause one or any combination of the following reactions. A force can cause an object to alter its shape, accelerate, decelerate, or change its direction.

21 Force A force is a derived unit, meaning that it is measured indirectly, by the effect it has on an object. According to Newton s Second Law, force is equal to the rate of change of the momentum(mass x velocity) of an object. The magnitude of a force is proportional to the rate it changes the object s velocity.

22 Force The unit of force in the imperial system is the Pound, which is also the unit of mass in the imperial system. The imperial system uses the LB-M and the LB-F to differentiate between mass and force, and the metric system uses the newton to identify force. Force = mass x acceleration

23 Weight Weight is a force exerted upon a mass due to its placement within a gravitational field. Although used interchangeably, the weight of an object differs from its mass. Weight is mathematically equal to the mass of an object multiplied by the magnitude of the gravitational field.

24 Pressure Pressure is the amount of force that is being applied to a single unit of area. When a force is evenly distributed over an area, the pressure at all points on that surface is the same. When a force is applied to an area greater than one square unit, the pressure applied is the amount of force acting on one unit of the area. Pressure = Force Area or lb-f/square inch

25 Atmospheric Pressure The earth is surrounded by an atmosphere that extends upward from its surface to a distance of est. 50kms. Air has mass so it is subject to the same action of earth s gravity, thereby exerting pressure on the earth s surface. The force exerted on one square inch of the earth s at sea level is lb-f

26 Work Work Energy Kinetic Energy Potential Energy Total Mechanical Energy Power

27 Work Work is the act of changing the energy content of an object or system. Mechanical work is done whenever a force acts upon an object, causing it to accelerate or decelerate through a distance. Work is a scalar quantity that is positive if the force acts in the direction of the object s movement, or negative if it opposes the movement of the object.

28 Work The amount of work done by a force is equal to the applied force multiplied by the distance through which the force acts. Since work is defined as a force that causes changes in movement, its units are foot-pounds of force.

29 Energy Energy is described as the ability of a substance or object to do work. Energy is required to perform some form of work, and an object is said to posses energy when it can do work. The energy of an object is classified by either Kinetic or Potential energy, or a combination of both.

30 Kinetic Energy Kinetic energy is the energy possessed by a moving object or substance. A falling object, a flowing fluid and moving machines all contain kinetic energy due to their motion. The amount of kinetic energy an object possesses is a function of its mass and its velocity. This energy can be used to perform work.

31 Potential Energy Potential energy is the energy an object possesses due to its relative position within a gravitational, magnetic, electrostatic or similar energy field. The amount of work an object can do as it changes its position is a measure of its potential energy. As an object is lifted from the ground the amount of work that can be done increase. W = F x s(distance)

32 Potential Energy This occurs also because a falling object generates a greater force as it accelerates in the gravitational field. The greater the force the greater the work that can be done. Spring energy is the potential energy of a resilient object due to it molecular and mechanical configuration.

33 Mechanical Energy The total mechanical energy of an object is equal to the algebraic sum of its kinetic and potential energies. Chemical, nuclear and thermal energies are other forms of energy that are stored in the molecules of substances and objects.

34 Power Power is the quantity of work done in a unit of time. Power is the rate of doing work. Power is equal to work divided by the period of time the work was done. The greater the amount of work performed during a unit of time, the greater the conversion of energy taking place or power being developed.

35 Power The power converted by a motor is calculated using the torque produced by the shaft in ft-lbs, and the rotational velocity of the shaft in radians per second. A common unit of mechanical power is the horsepower. One horsepower is the conversion of energy at a rate of 33,000 ft-lbf/minute.