Mechanical Advantage Worksheet

Work, Force and machines ( reading + questions )

Page 80. Qu: 1-5:

1. What is mean by :

a) Doing work is when you use force in any way(push/pull).
b) A machine is anything that makes work easier mainly because machines produce a much bigger force that humans.

2. Are you doing work when you are:

a) pushing a mover: Yes, because you are using force to make and object move recurring force.
b)cleaning your teeth: yes, because you're moving the tooth brush to move and clean your teeth correctly.
c)cycling: yes, because force is needed to make the paddle move then using gears and wheels the tires can also move which can make you go a long distance.
d) reading this page : no, because you're not using force to move a certain distance which can't produce any work( measured by joules/dxF) so, you're only using brain power.

3. Why must you eat if you are going to keep working?
- You must eat because any machine needs fuel to work and so our fuel is food which can make us work harder with more energy and we need energy to work in any form.

4. Why are spanners, pliers and can openers called machines?
- This is because by using a small force at one end a much greater force is produced at the other end.

5. Try to find out: the names of other simple machines:
-Lever
-Wheel and axle
-Pulley
-Inclined plane
-Wedge
-Screw


Page 81. Qu: 1-4:

1. What do you need to make a pulley system?
- One or more Pulleys and a rope/cable.

2. Give two reasons why it is easier for a mechanic to lift a car engine out using a pulley system?
- This is because the length of five ropes can each support the engine if the engine is 500n then each rope can support 100n equally.

3. What is the job of:
a) the chain: transmits the force to the back wheels, turning them.
b) the gears on a bicycle: change the number of times that one turn of the crankshaft turns the back wheels.


Page 82. Qu: 1-5:

1. Which simple machines were used:
a) to split the blocks: Wedges.
b) to move the blocks: Rollers.
c) to put the blocks in place: Ramps and Rollers.

2. a) How was friction reduced when the blocks were moved?
- By using the ramps or rollers avoiding the blocks to touch the ground and cause friction.
b)A simple invention, first used 700 years after the pyramid was built, would have reduced friction further. What is it?
- The wheel.

3. (DRAWING)

4. Wedge shaped tools and ramps are still in use. Give some examples of how they are used.

- Wedges:
1. Hold door, bicycle, engine parts in place.
2. Separate objects like blocks of cut stone.
- Ramps:
1. Wheel chars or any rolling objects help people get to higher/lower ground in all indoor facilities (malls).
2. Push or pull heavy object to a higher place ( ex. cars use them to get to another floor in parking areas with more than one floor.

5. How much work had to be done to raise the last block(weighing 25,000N) on to the top of the pyramid?
- A lot more work because the other blocks all were moved to the side or on top of each other, but the last on on top of the pyramid required much more force to push/pull on the ramps/rollers all the way on the top and it was a steep pyramid and the distance was much farther so, it needed more force, distance and work for the final block.

What a Machine is?

- A machine is any device that does any activity using energy which can also assist or make work easier. A simple machine is a device that helps make work easier; a device that makes it easier to move something, it also transforms the direction or magnitude of a force without consuming any energy. Some simple machines are a wheel, a pulley, a lever, a screw, and an inclined plane. Most machines consist of a number of elements, such as gears and ball bearings, that work together in a complex way. No matter how complex a machine, it is still based on the compounding of six types of simple machines. The six types of machines are the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw.

Forces

1.
- A Force is a pull or a push.

2. Examples:
- Friction:
Friction is a force which acts when two objects are rubed together. It acts to the opasite direction to movement. Friction causes objects to heat up and also causes their surfaces to wear away.
- Gravity:
Every object in the Universe attracts every other object in the universe. This invisible force for masses to move toward each other is called Gravity.
When you weight yourself, your weight may be around 30kg to maybe 50kg because of Gravity. Your weight is the result from the product of the force of gravity and the mass of you.Why two masses separated in space have a gravitational attraction to one another remains unknown, despite much research and various theories. These theories are listed on the left.
-Magnetic:
The force exerted between magnetic poles, creating magnetization is known as magnetic force. Every magnet has a north and south pole, just like the earth.Opposite poles attract so the north pole attracts the south pole and the south pole attracts the north pole. Like poles will repel (push away from) each other - so if you place two north poles together or two south poles together they will push each other away. A magnet's strength is strongest at the poles and weakest in the middle. The space around a magnet is called a magnetic field. It is this invisible area where the force of a magnet can be felt. For example, the closer you bring a paper clip to a magnet, the more you will feel the pull of the magnetic field. Just like what you did earlier.
- Nuclear Force:
The protons in the nucleus of an atom are positively charged. If protons interact, they are usually pushed apart by the electromagnetic force. (Remember, opposite charges attract, but like charges repel!). However, when two or more nuclei come VERY close together, the nuclear force comes into play. The nuclear force is a hundred times stronger than the electromagnetic force so the nuclear force may be able to "glue" the nuclei together so fusion can happen. The nuclear force is also known as the strong force. This is one of the four fundamental forces in the Universe. The nuclear force keeps together the most basic of elementary particles, the quarks. Quarks combine together to form the protons and neutrons in the atomic nucleus.

3. The units of force:
- Newtons, Dynes, kilogram-force(kilopond), pound-force, poundal.
More information on Units of Forces.

4. Equation of Force:
- Mass x Acceleration = Force.