The kicker has made contact with the football. in order for the ball to follow the path shown by the dotted line, what must be the true forces acting on the ball? a) force 1 must be the greatest. b) force 2 must be the greatest. c) force 3 must be 3the greatest. d) force 4 must be the greatest.

The correct option is b.

Explanation: When the kicker, kicks the football, it is applying force on the football.

From, the given image the applied force is in the upward direction, that is force 2 which is applied by the kicker.

Force 4 is the gravitational force which is equal to the weight of the football.

Force 1 is the reaction force on the kicker in order to kick the ball. This force should not be the greatest because if this would have been the greatest, the kicker would have fallen back. This force is balanced by the force 3.

Force 2 must be the greatest because the football is flying in the air due to the force applied by the kicker.

Hence, the correct option is b.

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.