UNIT 4: Machines

ACTIVITIES:

1.- Name three machines with one or few parts, and three machines with many parts.

·         One or few parts: the lever, the wheel, the inclined plane.

·         Many parts: a car, an aircraft, a train.

2.- Calculate the work required to lift a weight of 1200N to a height of 9m.

·         1200 x 9 = 10800 Joules required

3.- A person pushes a suitcase across a railway station of 20m. If the total performed is 1200J, how much force had to be applied?

·         1200/20 = 60N of force.

4.- Find out how many simple machines are combined in a wheelbarrow.

·         Two, the lever and the wheel.

5.- Complete the sentences:

a) Machines are objects that help save time and energy.

b) Planes and cars are compound machines.

c) All machines need energy to function.

6.- Complete a sentences of these objects where you describe the ENERGY that they use for.

a) vacuum: it uses energy to aspire dirt.

b) helicopter: it uses energy to move the rotor that make the helicopter fly.

c) stapler: it uses energy to insert the staples in the papers.

7.- You should always take care when using machines. Think of these machines that you can use and write how they can be dangerous and give a safety rule.

a) Knives: We can cut ourselves. We shouln´t play with them.

b) Plug: Children can put their fingers in them. Children must stay apart from them.

c) Jigsaw: We must be careful in order not to cut ourselves.

d) Glue pistol: It is very hot. We shouldn’t put our fingers on the glue.

e) Drill: We ought to be careful as we could harm ourselves easily.

8.- What sort of  SIMPLE MACHINES are these objects?:

 a baseball bat : a lever.

 the front of a ship : a wedge.

the fan blades : wedges.

 a toilet paper dispenser : a wheel.

 a door knob : a lever.

 a broom : a lever.

 9.- Find out the MACHINES that these objects got:

 Stapler: a) A lever b) A wedge

Wheel barrow:  a) A lever  b) A wheel

 10.- What category do the following levers belong to?

a) Screwdriver used to open a can. 1st class lever.

b) Fihsing pole. 3rd class lever.

c) Bicycle brake. 2nd class lever.

d) Balance. 1st class lever.

11.- The weight of a boy sitting on a see-saw(balancín) 1m from the fulcrum generates a force of 440N. How much force must his little sister produce if she sits 2m from the fulcrum?

         Fx2=440x1 -> 220N of force required

12.- A force of 5000N is required to lift a stone. However, if a 2m lever is availeble and it is placed with the fulcrum 25cm from the stone, how much force must be applied to the lever?

         5000x0.25=1.75xF -> 714.28N of force is required