Work
for work to be done on an object, what must happen to the object
must move something a distance as the result of a force
the ratio of output work to input work of a machine
mechanical advantage
What is the efficiency of a machine with 2000 J input and 500 J output?
25%
What's the unit for power?
W or Nm/s or J/s
Why couldn't the lazy student move the box?
No force
A worker pushes a lawn mower with 23.0 N at 60 degrees for 18.5 m. What is the work done?
212.8J
what is the mechanical advantage of a ramp that is 2 m high and 6 m long?
3
How much energy is required to get 100J of useful work out of a machine with 21% efficiency?
476 J
A worker pushes a lawn mower with 23.0 N at 60 degrees for 18.5 m for 60 s. What is the power?
3.5 W
Why did the lever break up with the fulcrum?
no support
A box is pushed across the floor 20 m using 15 N of force. What is the work done on the box?
300 J
what is the mechanical advantage of a that needs 15 N for force to output 300 N of force
20
How much useful work can be done with a machine with 15% efficiency if 3600 J of energy is put into it?
540 J
Hoover Dam generates 2000000 kW of power daily. How much work is done in one day?
1.7 x 10^14 J
Anti-gravity
Four students push the football sled 5 m using 1,000N. What is the work done on the football sled.
5000 J
If a machine has a MA of 3.5 and you apply 400 N, what's the max weight it can lift?
1400 N
How high up is a 1200 kg ski lift pulled if a 20% efficient machine uses 3,850,000 J of energy?
64 m
A 1500 kg race car can go 25 m in 5 s. What is the power required to do this?
73500 W
Why did the force get tired?
Too much work
What is the work done on an object that is moved 300 cm with 6.2 N of force?
18.6 N
An effort of 350 N is applied to an ideal machine. The effort force moves a 900 N object a certain distance. What is the mechanical advantage?
2.6
What is the output work of a machine that is 75% efficient and has an input work of 180 J?
135 J
A crane lifts a load of 1000 kg a vertical distance of 25 m in 9.0 s. How much power is produced?
27,222 W
What do you call 1 kg of falling figs?
1 Fig Newton