Scientist
We're going to talk about the problem of lifting a weight. In lifting a weight there are 3 things to consider, gravity friction and a power source. First friction.
Girl 1
Courtney can not fly because of gravity and not weight.
Girl 2
Courtney is now in the air.
Girl 3
Courtney can not get back up in the air with out us.
Scientist
This force is called gravity, you can not stay in the air beacause of it.
Boy 1
I'm Hungry.
Boy 2
Here have a bannana.
(boy throws skin on floor)
Boy 3
Woah mind that bannana!
(boy 4 falls over)
Scientist
Friction happens when 2 surfaces meet causing them to slow down, however we can reduce friction by lubrication and that is why he slipped on the banana skin. Next the power source.
Boy 4
Woah.
Girl 4
Oi you two stop fighting.
Scientist
Water pistols are good for fun but they can also be used as a power source.
Girl 4
Places balloon on floor.
Girl 5
Moves balloon by squirting water at it.
Scientist
When we use water to move things it's called hydraulics.
I am going to lift the weight but this time I am not using hydraulics.
I am using muscle power with this pulley to make it easier. I am going against gravity and there is friction between the rope and the pulley. It needs to be high enough to stop the rope slipping but low enough for me to pull it.
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