~lever
~fixed pulley
~inclined plane
~block and tackle
~ a human tower
Cleaning out the barn and storing equipment. This group joined together to make work easier! Their last task is to lift a barrel of nails up to the windows you see here over the barn door. They have several options to complete this task. What is the best choice? Why?
A) A human tower. It will let everyone help and it will be fun.
B) An inclined plane. You can roll the barrel instead of lifting. You move the barrel a greater distance but use less force.
C) A first class lever. In this case, you would push down to move the barrel up. Using a lever would require less force than lifting the barrel using a pulley.
D) Block and tackle. A system of pulleys working together multiplies force in addition to changing the force's direction, meaning less force is required to move an object.

alfred von schlieffen, german army chief of staff, was given instructions to devise a strategy that would be able to counter a joint attack. in december, 1905, he began circulating what later became known as the schlieffen plan. schlieffen argued that if war took place it was vital that france was speedily defeated.

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.