sYSTEMS
SIMPLE MACHINES
work/force/energy
Calculations A
Calculations B
100
name a system that is 100% efficient
NONE
100
How can you create a mechanical advantage with a 3rd class lever?
-can’t. no advantage
100
if a person pushes a car but it doesn’t move. how much work is done? why?
- none. without movement there is no work done
100
A force of 800N is needed to push an object. You move it 40 m. how much work is done?
-32000 J
100
What is the mechanical advantage of this pulley system?
4
200
How is efficiency measured?
-(output / input) x 100
200
how does the shape of the wedge change its effectiveness
-the sharper the point, the more effective the wedge
200
name 3 ways a machine makes work easier
- Change the amount, the speed, or the direction of force.
200
Calculate the mechanical advantage of the wedge if it is 12 cm wide and 20cm long
20/12
1.666
200
Calculate the mechanical advantage of a wheel&axle if the axle is 5 cm wide and the wheel is 10 cm wide.
rw/ra
5/2.5 = 2
300
name the 4 factors we look at in any system
- function, input, output, secondary effects
300
What is a screw and how does it help us work?
-inclined plane wrapped around a pole/itself
-multiplies the rotational force into linear force
300
A wind turbine uses 410,000J of energy and creates 270,000J of power. What is the efficiency of the turbine?
-65.8%
300
calculate the mechanical advantage of the machine if it is 20cm long and the load is 5cm from the fulcrum. what kind of machine is this?
20/5 = 4
LEVER
300
calculate the mechanical advantage of the machine if it is 8cm tall at one end, and 16 cm long. what kind of machine is this?
16/8
= 2
inclined plane
400
How can friction be both a positive and negative force?
-positive for giving traction.
-negative by creating more work
400
How does the size of a wheel and the size of the axle change its effectiveness?
-larger wheel and smaller axle = easier, so less force is needed by maximizing the difference between
400
you are lifting 50N boxes onto a shelf that is 1.5 m high. you can move 4 boxes a minute. How much work is done in 15 mins
- (50N x 1.5m) x 4 box/min
- x 15mins = 4500J
400
The mechanical advantage of a lever is 6. How much input force was needed to lift a force of 320 N?
53.333N
400
A horse pulls a cart around a circular track with a diameter of 1 km. Using an average force of 800N.
How much work is done for one lap of the track?
2512000 J