2006-10-15 07:54:51 · 5 answers · asked by pinkpaperdoll♥ 2 in Education & Reference ➔ Homework Help
a kid at the edge of an 18.5m rooftop throws a ball straight up so that it just misses the bulding as it falls to the street. the ball is in the air for 2.79seconds. complete the data table and determine the initial velocity.
datas:
initial velocity: ?
final velocity: 0
displacement: -18.5
acceleration: -9.8m/s/s
time: 2.79seconds.
why is the displacement negative?
2006-10-15 08:02:30 · update #1
i dont need the initial velocity.. i just need to know why the displacement is negative..
2006-10-15 08:20:00 · update #2
the displacement is negative because the initial direction was up therefore being the positive direction. the ball would have finished on the ground (the opposite direction from the initial direction)hence why the answer is negative. here is a better example.
if you were in a car, left form your driveway and travelled 7 miles to school. stayed at school all day then travelled 7 miles home again and parked in the same driveway you would have travelled 14 miles but your displacement would be zero.
if you were to carry on driving up your drive into the garage your distance would increase but since you are further BACK your drive your displacement would then be negative. as you have technically gone backwards from the starting point.
another scenario is that if you parked a mile down the road at a friends your displacement would be 1 mile (from the starting point).
SO... the conclusion is that you never ever go any where as long as you return to the place you began but the distance you travel never resets its self it goes on and on and on and on!!!
i really hope this helps you i have done A level physics so i know what its like!
2006-10-16 09:08:36 · answer #1 · answered by redhackle13 1 · 0⤊ 0⤋
You say that the ball is at zero displacement where you are holding it on top of the building to begin with. You throw it up first which is positive displacement but then it falls down below where you are standing, which is negative displacement.
2006-10-15 22:58:15 · answer #2 · answered by keri s 2 · 1⤊ 0⤋
Draw a diagram of the displacement and then sketch a coordinate (x-y) axis over it. The displacement is negative if it moves down or to the left in the coordinate axis.
2006-10-15 07:58:01 · answer #3 · answered by Anonymous 3 · 0⤊ 0⤋
initial velocity: ? ====>>> 4.16m/sec
final velocity: 0
displacement: -18.5m
acceleration: -9.8m/s*s
time: 2.79seconds.
is this answer matched with urs.
2006-10-15 08:17:38 · answer #4 · answered by rajesh1040 2 · 0⤊ 0⤋
stop cheating and just admit to your child that you dont know.
2006-10-15 08:04:15 · answer #5 · answered by Anonymous · 0⤊ 2⤋