Sign Qty

help please?

which of the following set of forces cannot have a vector sum of zero?
A.10,10,& 10 lb B.10,10,20 lb C.10,20,20 lb D. 10,20,40 lb

2.Which of the ff. sets of displacements might be able to return the car to its starting point?
A. 2,8,10,25km B. 5,20,35,65km C. 60,120,180,240km D. 100,100,100,400km
3. As an airplane climbs,.... A. wt. increase B. wt. decrease
4.w/c of the ff. is an example of a vector qty?
A. tension B. wt. C. force D. length
5. What is wrong with this road sign: BOSTON 7mi (11.263km)
A. suggest that the distance inside the () is its equivalent
B. the distance is being multiplied C. BOSTON maybe of diff. distance D. the place has English and metric citizens
6.an airplane whose airspeed is 200km/s is flying in a wind of 80km/h. The speed of the airplane relative to the ground must be between ___ and ____.
7. which of the ff. pairs of displacements cant be added to give a resultant displacement of 2m?
A. 1m & 1m B. 1m & 2m C.1m&3m D. 1m&4m

1) D Reason: for a vector sum to equal 0 it must create a triangle, D is the only one that doesn't.
2) C Reason: 180^2 + 180^2 = 240^2 makes a pythagorean triangle, none of the others do.
3) B Reason: As you get farther from the center of the earth gravity decreases.
4) C Reason: A and B are types of Forces and length is just distance, speed is a vector.
5) A Reason: 7 miles is 11.6667 km. (D could be plausible, but isn't the scientific answer)
6) I'm not really sure what this answer wants. 1) 200 km/s is impossibly fast. the only answer I got was changing 80 km/h to km/s and got 199 km/s and 200 km/s. 2) or 719900 km/h and 720000 km/h
7) B and D are both answers. Reason: 1+1=2; 2+1=3 or 2+(-1)=1; 3+(-1)=2; 4+(-1)=3
Hope this helps... Normally I try not to help people with their own work. but I'm bored

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