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Another question about projectile motion

  • Thread starter physics=headache
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  • #1
physics=headache
A stunt man jumps from the top of one building to the top of another building 4.9 m away. after a running start, he leaps at an angle of 16 degrees with respect to the flat roof while traveling at a speed of 5.1 m/s. the other roof is 1.9 shorter than the building from which he jumped. i have to find out his vertical displacement upon reaching the front edge of the lower building with respect to the taller building.

heres my thoughts on what to do: i can use 16 degrees and 5.1 m/s to find the x and y component of the initial velocity. that's all i've got so far.

any help would be appreciated
 

Answers and Replies

  • #2
1,036
1
i can use 16 degrees and 5.1 m/s to find the x and y component of the initial velocity
Right. So what's the problem? Once you've done that, how long does it take him to travel 4.9m horizontally? Then, given his initial VERTICAL velocity, what is his vertical displacement after that length of time?
 
  • #3
physics=headache
still can't get it

ok i got that, but where does the 1.9 m come in?
 
  • #4
1,036
1
Presumably it's there to help you learn to distinguish between relevant and extraneous information. :smile:
 
  • #5
91
0
Originally posted by gnome
Right. So what's the problem? Once you've done that, how long does it take him to travel 4.9m horizontally? Then, given his initial VERTICAL velocity, what is his vertical displacement after that length of time?
y(t) = -9.81*t^2 + Voy*t + 1.9m

The jumpers initial height is 1.9m.
 
  • #6
enigma
Staff Emeritus
Science Advisor
Gold Member
1,747
10
Nope,

the height you need to find is with respect to the taller building.

The 1.9m is there because either:

1) The jump isn't enough to clear the gap.

or

2) It's there to trip you up with extraneous information.
 
  • #7
1,036
1
Presumably it's there to help you learn to distinguish between relevant and extraneous information.
When I fire from the hip, I tend to shoot myself in the foot.

Working out the actual numbers, it seems that when he reaches the second building, his vertical displacement
is -3.49m; i.e. his feet hit the wall 1.59m (3.49-1.9) below the roof. That's where the 1.9m height difference comes in.
 
  • #8
42
0
you could find the solution in the Haliday and Resnick book (plane motion). It is solved there.

hhegab
 

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