IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: helai.j on October 09, 2010, 12:51:41 pm
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No one seams to answer my Questions when i post in the specific topics so, i guess no harm trying here :)
can anyone answer these 2 Questions for me please ? i dont need just the answers i want to know how they are done . thanks
1) A movie stuntman with a mass of 90 kg stands on a stationary 1 kg skateboard. An actor shoots the stuntman with a 9 mm pistol. The 8-gram bullet leaves the pistol at 358 m s?1 and embeds completely in the stuntman’s bulletproof vest. At what speed will the stuntman roll away?
2) In a stunt for an action movie, the 100 kg actor jumps from a train which is crossing a river bridge. On the river below, the heroine is tied to a raft floating towards a waterfall at 3 m s?1. The raft and heroine have a total mass of 200 kg.
a If the hero times his jumps perfectly so as to land on the raft, and his velocity is 12 m s?1 at an angle of 80° to the river current, what will be the velocity of the raft immediately after he lands? Draw a vector diagram to show the momentum addition. (Ignore any vertical motion.)
b If the waterfall is 100 m downstream, and the hero landed when the raft was 16 m from the bank, would they plummet over the fall? (Assume the velocity remains constant after the hero has landed.)
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1) A movie stuntman with a mass of 90 kg stands on a stationary 1 kg skateboard. An actor shoots the stuntman with a 9 mm pistol. The 8-gram bullet leaves the pistol at 358 m s?1 and embeds completely in the stuntman’s bulletproof vest. At what speed will the stuntman roll away?
since momentum is always conserved
(8/1000)*358=(90+1)*V
V=0.03147m/s
i find this speed weird !
is it right?
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yes that one is correct, thank you :)
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yes that one is correct, thank you :)
:D you are welcome
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2) In a stunt for an action movie, the 100 kg actor jumps from a train which is crossing a river bridge. On the river below, the heroine is tied to a raft floating towards a waterfall at 3 m s?1. The raft and heroine have a total mass of 200 kg.
a If the hero times his jumps perfectly so as to land on the raft, and his velocity is 12 m s?1 at an angle of 80° to the river current, what will be the velocity of the raft immediately after he lands? Draw a vector diagram to show the momentum addition. (Ignore any vertical motion.)
b If the waterfall is 100 m downstream, and the hero landed when the raft was 16 m from the bank, would they plummet over the fall? (Assume the velocity remains constant after the hero has landed.)
I was looking for astar's post but failed. I tried, I'm not sure but this took me 15 mins only to figure out the entire scene ::) :P
a) So perependicular to river's flow. Y component velocity
100X 12sin80+ 200X0= (100+200)v
v=3.94m/s
^^speed to the bank...sidestream
Parallel to river's flow. X component of velocity
100X12cos80+ 200X3= (100+200)v
v= 2.69m/s
^^speed to the waterfall...downstream
b) Time taken to reach the bank= 16/3.94 = approx 4s
Time taken to reach the falls= 100/2.69=approx 37s
the raft will this reach the bank safely.
I'm not sure. -.-
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I was looking for astar's post but failed. I tried, I'm not sure but this took me 15 mins only to figure out the entire scene ::) :P
a) So perependicular to river's flow. Y component velocity
100X 12sin80+ 200X0= (100+200)v
v=3.94m/s
^^speed to the bank...sidestream
Parallel to river's flow. X component of velocity
100X12cos80+ 200X3= (100+200)v
v= 2.69m/s
^^speed to the waterfall...downstream
b) Time taken to reach the bank= 16/3.94 = approx 4s
Time taken to reach the falls= 100/2.69=approx 37s
the raft will this reach the bank safely.
I'm not sure. -.-
Well.....it seems good to me :)
The last answer was obvious. Hero and heroine always comes out alive :P
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Well.....it seems good to me :)
The last answer was obvious. Hero and heroine always comes out alive :P
Looks good...seems good....i...don't...know...if...it....actually...is....the....right....answer :P
HAHAHA.....If it's a bollywood movie...then we can be 100% sure :P
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Looks good...seems good....i...don't...know...if...it....actually...is....the....right....answer :P
HAHAHA.....If it's a bollywood movie...then we can be 100% sure :P
Hehe.....don't worry we'll get to know that soon.
If it is the right answer.......then hats off to you :)
If it is not.......then we'll have to find another way to get it ;)
Yeah......... :D
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the b part is correct but A isnt, that answer is attached bellow
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the b part is correct but A isnt, that answer is attached bellow
LoLzzz ;D
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LoLzzz ;D
^^ditto :P
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here
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haha i didnt notice wat i attached ! LOL sorry guys here it is
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here
Big thanks to the member of the month :D