16. Mechanical Comprehension Flashcards
What is the equation for weight?
weight = mass * gravity
In physics, what changes the velocity of an object?
By applying force upon the object.
What is the mathematical formula to determine force?
Force = Mass * Acceleration
Describe the action and reaction third law of motion by Newton.
For every action in nature, there is an equal and opposite reaction. YOU HIT ME FIRST!
What is the idea of equilibrium?
A very basic concept when dealing with forces is the idea of equilibrium or balance. When two or more forces interact so that their combination cancels the other(s) out, a state of equilibrium occurs. In this state, the velocity of an object does not change. The forces are considered to be balanced if the rightward forces are balanced by the leftward forces and the upward forces are balanced by the downward forces.
What is a static equilibrium?
If an object is at rest and is in a state of equilibrium, then it is at static equilibrium. Static means being stationary or at rest. For example, a glass of water sitting on a table is a t static equilibrium. The table exerts an upward force on the glass to counteract the force of gravity.
What is pressure?
Pressure is the measurement of force over an area. Pressure is usually measured in pounds per square inch (psi).
What is the formula deriving pressure?
Pressure = Force (in pounds) / Area (in square inches)
If 50 pounds of force is exerted on 10 square inches of surface, the amount of pressure is 5 pounds per square inch (5 = 5/10)
What is a barometer?
A barometer is a gauge that measures atmospheric pressure. Normal atmospheric pressure is 14.7 psi. A change in air pressure means the weather is about to change.
What are some of the common forces that act on objects?
- Gravity is the physical property that draws object toward the center of Earth (and other objects that have mass), which is generally known as weight. Gravity generates a weight force when multiplied by an object’s mass.
- Applied force is force a person or another object applies to an object through contact.
- Tension is transmitted through string, rope, cable, or wire when forces are acting on opposite ends.
- Friction is resistance to the motion of two objects or surfaces that touch.
- Recoil occurs when something regains its original form when an object exerting force on it is removed; it is also referred to as a spring force.
- Magnetism is the property of attracting iron or steel
- Static electricity is the production of stationary electrical charges, often the result of friction.
Explain Newton’s law of universal gravitation.
Newton’s law of gravitation states that every object in the universe attracts every other object in the universe. Earth produces gravity, and so do the sun, other planets, your car, your house, and your body.
The amount (force) of the attraction depends on the following, what are those?
- Mass: The force of gravity depends on the mass of the object. If you’re sitting in front of your television, you may be surprised to know that the television set is attracting you. However, because the mass of the TV is so small compared to the mass of Earth, you don’t notice the physical “pull” toward the television set.
- Distance: Newton’s law also says that the greater the distance between two objects, the less the objects attract each other. In other words, the farther away an object is from Earth (or any other large body), the less it weighs. If you stand at the top of a high mountain, you’ll weigh less than you will at sea level. Don’t get too excited about this weight-loss technique, thought. The difference is incredibly small. Gravitational pull isn’t the next big diet craze. Sorry!
What is a tension force?
Tension force is the force transmitted through a rope, string, or wire when force is applied to both ends. The force is the amount of tension directed along the rope, string, or wire and pulls equally on the objects at both ends. Tension force is usually measured in either pounds-force (lbf) or newtons (N); 4.45 newtons equal 1 pound-force.
What is elastic recoil?
Liquids and gases don’t have a specific shape, but solid matter does. Solids are perfectly happy with the way they look and resist changes in shape. If you exert a force on a solid shape, it responds by exerting a force in the opposite direction. This force is called elastic recoil aka. spring force.
What is the equation for Spring force?
Spring Force = Spring Constant * Distance Displaced
What is magnetism?
Magnetism comes from the force (attract or repel) the magnet cause. The type of magnetism you’re probably most familiar with is ferromagnetism, which involves iron; it is the strongest type.
What is static electricity?
When you rub a balloon on your little brother’s head and then touch the balloon to the wall, chances are that it’ll stick. That’s due to electrical force. This kind of force, called static electricity, is the buildup of electrical charges on the surface of a substance. Opposite electrical charges attract, so the charge on the balloon and the charge on the wall are literally pulling for each other.
What are drag forces?
Drag forces slow down objects; the amount of drag depends on an object’s shape and the substances it’s moving through, such as air or water. If you have ever held your hand out of the car window horizontally, then rotated it vertically, you’ve experienced the increase in drag forces that pushed your arm backward. Designers make cars and boats as streamlined as possible to reduce drag, making these vehicles as efficient as possible. (If your drill sergeant at basic Combat Training calls you a “high-speed, low drag” troop, it’s a compliment — but don’t respond with “Thanks!” Trust me on this one.
What is work, really?
Mechanically speaking, work happens when a force (usually measured in pounds) moving over a measurable distance (usually measured in feet) overcomes a resistance. In the United States, the unit of measure for work is often called a foot-pound. (Note: the rest of the world uses the newton-meter, or joule). one foot-pound of work occurs when a 1-pound weight is lifted to a height of 1 foot. You can represent this concept inequation form.
Work = Force * Distance
Work is different from effort; work is the result of effort. You can think of effort as being force and of work as being what you produce with that force.
What is the difference between potential and kinetic energy?
Energy is the capacity to do work. Every object in the universe has energy, and it is either potential or kinetic. Potential energy is stored energy — energy that is not doing anything at the moment but that’s in the object by virtue of its position in a field. If this book is resting in your hands right now, the book itself is holding potential energy. If you raise the book over your head, you’re increasing its potential energy (thanks to the Earth’s gravitational pull). When you accidentally drop it, all its potential energy becomes kinetic energy, or energy of motion. When the book hits the ground, its energy becomes potential again.
What is inertia?
An object’s tendency to resist change in its state of motion is called inertia.
What is power? display it in mathematical expression.
Power is the rate at which word is done. Mathematically speaking,
Power = Work/Time
In this formula, work is usually measured in joules, time is measured in seconds, and power is measured in watts.
What is horsepower?
In many machines, power is measured in joules, time is measured in seconds, and power is measured in watts.
In many machines, power is measured in horsepower, which you may be more familiar with than watts and joules. Using the same formula to calculate horsepower requires you to measure work in foot-pounds, time in minutes, and power in foot-pounds-per-minute. Horsepower is derived from the estimate that an average horse can do 33,000 foot-pounds of work in 1 minute. Therefore, 1 horsepower = 33,000 foot-pounds per minute. One horsepower is also the same as 550 foot-pounds per second, which is equivalent to 745.7 watts.
What is a mechanical advantage? Express in mathematical terms.
Machines give you the ability to magnify and change the direction and magnitude of forces (such as a lever). When a machine multiplies the force you use, it gives you a mechanical advantage. This concept can be stated as:
Mechanical Advantage = Resistance/Effort = Output Force/Input Force
Some simple machines may give you a mechanical advantage of 1 or 2. This means that they enable you to do one or two times the amount of work by expending the same effort. but those simple machines are still worth using! Often, even if a machine doesn’t multiply your effort (or doesn’t multiply your effort by much), it can at least spread your effort out and make it more effective.
Differentiate fulcrum, resistance arm, and the effort arm of a lever.
All lever work by using a fulcrum (point of support) to reduce resistance and multiply the effect of effort. Resistance (such as a weight force from an object with mass) is exerted at one end of the lever (the resistance arm) and effort is exerted at the other (the effort arm). The effort arm moves the resistance arm.
What formula do you have to use in order to determine how much a lever reduces the amount of effort needed to do work?
Length of Effort Arm/Length of Resistance Arm = Resistance Force/Effort Force
What is the mathematical expression of the mechanical advantage using a lever?
Mechanical advantage = Effort Arm/Resistance Arm
Levers fall into classes, what are those? Synthesize.
Levers fall into classes: 1, 2, and 3. A Class 1 lever’s fulcrum is between the effort and load. Scissors, pliers, old-school seesaws, and the oars on a boat are examples of Class 1 levers. With a Class 2 lever, the load between the effort and the fulcrum; think wheelbarrows, crowbars, and nutcrackers. The fulcrum on a Class 3 lever is beside the effort and opposite the load. Tweezers, staplers, and brooms are all Class 3 levers.
What is an inclined plane?
The inclined plane, also called a ramp, is another very simple machine that makes moving an object from one point to another easier. The ramp spreads your work out over a longer distance, so less force is needed to do the work.
How can you express in mathematics the advantage using a ramp or an inclined plane?
Length of ramp/Height of ramp = Weight of object being moved/Force required to move object.
What are wedges?
Wedges are form of inclined plane and can multiply your effort in much the same way as ramp can. Screws are also inclined planes, only in spiral form. Screw jacks, which you can use to lift your house up to build a new foundation, are a combination of a lever and an inclined plane.
What pulleys and gears?
Pulleys and gears are simple machines that can be used to change the magnitude (size) and direction of force. When you ride in an elevator, step onto an escalator, drive your car, or wind your watch you’re using pulleys and gears.
Describe the block and tackle arrangement.
When used in block and tackle arrangement, pulleys make lifting heavy objects easier. In block and tackle systems, pulleys can also be used to change the direction of your pull. If you tie a 200-pound crate to one end of a rope, run the rope through a pulley, and grab the other end of your rope, you can pull down on the rope to lift the crate up. Without a pulley, you could pull down on the crate all day, and it wouldn’t go up. In this case, using a simple pulley, the force of your pull must equal the weight of the object being lifted. The regular pulley doesn’t multiply your force, but it makes the process of lifting easier by allowing you to redirect the force.
What are gears?
Machines often use gears to transmit motion from one place to another. An additional advantage of using gears is that they can be used to change direction, increase or decrease speed, or increase or decrease force. Gears arranged in a series turn in the opposite direction of each other. If you have an even number of gears connected in a series, the first and last gear turn in opposite directions. If you have an odd number of gears aligned in a series, the first and last gear spin in the same direction.
What are bevel gears?
When gear shafts aren’t parallel to one another, bevel gears can be used to connect shafts at different angles. The principles of gear rotation remain the same. A car’s differential which takes a drive shaft rotating along the length of the car and sends power 90 degrees out to the rear tires, is an example of a bevel gear.
In addition to magnifying force as part of a block and tackle system, pulleys have another use. When connected by a system of belts, pulleys can…
Drive other pulleys.
Like gears, pulleys are used to transmit motion from one location to another. However, the physical properties of pulleys are different from those of gears.
Turning Direction
&
Speed Rotation
Describe why the physical properties of pulleys are different from those of gears.
Turning direction: Unless the driving belt is reversed (twisted), pulleys connected in series rotate in the same direction.
Speed of rotation: Although the speed of gear rotation is determined by the number of teeth, how fast a pulley rotates depends on the diameter of the pulley in relation to the diameter of the pulley that is driving it.
How does the wheel-and-axle multiply the effort you use?
The wheel-and-axle machine multiplies the effort you use, producing a greater force. When you steer a car by using a steering wheel (which is a wheel-and-axle device), a little effort exerted on the steering wheel turns the wheel of the car in the direction you desire.
What is the difference between static torque and dynamic torque?
Torque can be static or dynamic. Static torque doesn’t produce an angular acceleration — it’s what happens if you push on a door marked “Pull,” or pedal your bike at a constant speed without accelerating. Dynamic torque produces an angular acceleration, and it’s what you see when a racecar takes off down the track.
What are vises in mechanics?
Although many mechanisms are designed to transmit motion, some machines have the purpose of keeping things motionless. Vises are very useful because they can close around items and hold them with great force (much greater force than you could do by holding the item in your hands).
What is a hydraulic jack?
A hydraulic jack uses nearly incompressible liquid, such as oil, to exert force in order to move an object.
