Science Review Sheet

Here are most all the concepts we have covered and learned about. 

How can you give friction the slip?

1. slide
2. ice rink
3. curling

Do rollers make work easier?  Why? Rollers placed under a load reduce contact surface between the load and the floor.  This reduces friction.  Less friction means that less effort is needed to move the same object

 

Name 4 ways we use “rollers” everyday.

1. Conveyor belt
2. Toilet paper roll
3. Steam roller

Rolling pin

Will a load moved on rollers and a load moved on wheels be able to complete a slalom race in the same amount of time? NO – the wheels will win because they are able to TAKE the load with them; where you need to go with the load on rollers. 

 

 

Machine: a device that helps us to do work.

Force: a push or a pull action.

Friction: is a force that slows down motion between two objects that touch.

There is LESS friction between smooth surfaces than between rough surfaces.

Work: is the result of a force moving an object.

Fixed Pulley System: a pulley that is stationary and changes the direction of the force (makes it easier because you get to pull down)

Load: an object that needs to be “moved”

Effort: the amount of force used.

Gears: wheels with teeth that interlock to give off energy

Fulcrum: the supporting point of a lever, also called a pivot

Pivot: an object that allows something to “move” slightly

A third class lever is a lever in which the EFFORT is in between the LOAD and the FULCRUM.

A first class lever is a lever in which the FULCRUM is in between the LOAD and the EFFORT.

A second class lever is a lever in which the LOAD is in between the EFFORT and the FULCRUM.

Two examples of a 1st class lever: seesaw and prybar.

Two examples of a 2nd class lever: wheelbarrow and nutcracker.

Two examples of a 3rd class lever: tweezers and stapler.

 

 

 

In a wheel to wheel drive system, will both wheels turn in the same direction? No, the wheels turn in opposite directions b/c they are touching.

In a belt drive system, when do the wheels turn in the same direction?  When the belt is around them in a “straight” line.

 In a belt drive system, when do the wheels turn in the opposite direction?  When the belt is crossed in a figure 8.

In a belt drive system does the size of the driver wheel affect the rate at which the driven wheel is turned?  (“Change the Driver” experiment) Yes, smaller wheels will rotate more times than a big wheel will in one rotation.  Whereas if the small wheel is the driver, the larger wheel will not go around a full rotation compared to one rotation of the smaller wheel.

 

How are dominoes like simple machines? They transfer energy from one to another.

In a gear drive system, do gears of different sizes affect the speed of the driver gears (“Gear Together” experiment) ___________________________________________ ____________________________________________________________________________________________________________________________________

Does changing the size and number of gears in a system affect the speed and direction of the gears? _______________________________________________________ ____________________________________________________________________________________________________________________________________________________

Does changing the position of the fulcrum affect the force needed to carry a load? Yes, you need more force to lift a load as the fulcrum gets closer to the effort.

Does changing the location of the effort on a third class lever affect its performance? Yes, a 3^rd class lever is most effective when the effort is close to the load.

In a 2^nd class lever, as the load moves closer to the fulcrum, is more or less effort required to lift the load? As the load gets closer to the fulcrum, there is less effort required.

Do pulleys make raising an object easier? YES! – b/c I can use my body weight.

Will the use of a pulley reduce the amount of force required to lift a load?  NO – but it changes the direction (pulling down)

 

Will a moving pulley affect the effort required to lift a load?  (Single Movable Pulley experiment) YES! – it reduces the effort in half. –refer to comparison sheet.

Does a fixed & movable pulley system affect the effort required to life a load? (Single Fixed & Single Movable Pulley experiment) HINT HINT HINT *** be able to draw a labeled picture of this pulley system** S.M. – reduces the effort; S.F. – changes the direction

Will the placement of the axle in the wheels change the efficiency of the vehicle? Yes.  The best place for the axle is in the middle of the wheel so that the wheel turns evenly.

 

Where will the largest movement in a wheel and axle occur – in the axle or in the wheel? WHY? The axle has to work harder b/c it is smaller than the wheel; therefore it rotates more times than the wheel does in one rotation.