Work and Machines

P.80 Q.1-5
1.
a) Say that doing work is using a force to move an object.
b) A machine is anything which makes it easier to do work.

2.
a) Yes, because you are pushing the mower.
b) Yes, because as you are cleaning your teeth you are pushing and pulling the tooth brush.
c) Yes, because you are pushing on the pedal of the bike.
d) No, because you are not moving will reading the paper.

3. Your body needs chemical energy to be able to do any work.

4. Spanners, pliers, and can openers are called machines because in each one of them you have to push or pull.

5. Wedge, Inclined plane, Ramp, etc.

P.81 Q.1-4
1. To make a pulley system you need a pulley and a rope.

2. It is easier because the distance is more so the force he is pulling is less also it is easier because you can use your own wait.

3.
a) A chain passes on the force to the back wheels, turning them.
b) The gears change the number of times that the crankshaft turns the back wheels.

4. The difference between high gear and low gear is that high gear ha smore distance and it is easier to cycle on then low gear.

P.82 Q.1-5

1.
a) Wedges were used to split the blocks. Holes were cut in the rock and wooden wedges were hammered in. When water was poured over the wedges the wood swelled, splitting the stone.
b) Barge-like boats were used to transport the blocks up the river. These were towered by large boats which were driven by sails and oars.
c) The slaves had to pull them up huge ramps of earth. Of course they had to build the ramps first of all.

2.
a) The friction was reduced because there was less contact between the wheel and the ground.
b) A pulley

3. Sir, the picture couldn't upload.

4. One example of a wedge shape tool is a knife and it is used to cut things. A ramp is used today to for wheelchairs.

5. 25000x140= 3500000