question 3 on page 82

Building a Pyramid Pg.82

1. a) When split the block the builders had to use wedges so they can be two parts at lest. b) To move the blocks from a place they had use ramps and rollers which are incline plane and wheel.
   c) The ramps and rollers were used to place the blocks in place .
2. a) Friction was reduced when the blocks had be moving by the simple machines since the force was reduced when using a simple machine then by your body force. b) After the pyramids were built by 700 years people invented the pully
3. At a new post
4. Some example of wedge would be : Ax, Knife, Nail Cutter and Scissors. Some examples for ramps that are used today are: ramps that are added at the end of a pulling car, hills, and escalators.
   

Pg. 81 Answers

1. Ropes and pulley wheels are needed when doing a pulley system.
2. Some of the reasons that the mechanic will find the pulley a good machine to help left the car engine since he will be using less force to pull up the car engine . Another reason is that it is easier to left the car engine because it is supported by the ropes and the wight of the person pulling it.
3. The chain runs over the small / large cog wheel at the back so that one turn of the crank turn the back wheel. The cycle's gear changes the number of times that one turn of crankshaft turns the back wheel.
4. The difference between low gear and high gear is that the low gear you ride with it when climbing a hill and the with every paddle the back wheel moves one than once while the high gear is when you ride with it

Work and machines p. 80

Questions 1-4

1.a) What is meant by "Doing work" is using a force to move an object.

b) A machine is anything which makes it easier to do work.

2.a) When pushing a mower you are doing work since you are pushing something , doing a movement and using force with some distance.

b) Using some force and distance you are doing work while brushing your teeth

c) In cycling you are doing work since your leg has to paddle and move then it is part of work.

d) Reading page it not work , the only thing that i have to do to read this page is look at it with my eyes.

3.When we work we use up energy which is given to us be food.

4. Spanners , Pliers and can openers are meachines because all of then has the action of a lever in it.

From times immemorial, man has used machines to help him in his work. Today, we are dependent on machine for almost every task. When we think of machines we always tend to think of big and complicated units with many moving parts like wheels and rollers and gears and shafts. A bicycle is a machine which is used to gain speed. We gain speed by exerting additional force. When we try to ride a bicycle up a steep hill, we soon realize that we gain speed by applying greater force. It is impossible to multiply both the force and gain the speed at the same time.

force

A force is a pull or a push some examples of forces are gravity, friction , electrostatic and nuclear force. Newtons is the measurement that is used to measure force. Force's formula is :

force= mass x acceleration.