# Can you help with this physics question?

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#1
the question says:
how far does a dropped pencil case fall in 0.25 seconds? It accelerates downwards at a speed of 9.8ms^-2.
the answer must be to 2sf

my method was to do acceleration=speed/time to find the speed, then speed = distance/time to get (9.8*0.25)*0.25=0.61. apparently, however, this is wrong. what was my mistake?

thank you 😁
0
3 years ago
#2
(Original post by khasali)
the question says:
how far does a dropped pencil case fall in 0.25 seconds? It accelerates downwards at a speed of 9.8ms^-2.
the answer must be to 2sf

my method was to do acceleration=speed/time to find the speed, then speed = distance/time to get (9.8*0.25)*0.25=0.61. apparently, however, this is wrong. what was my mistake?

thank you 😁
You need to use the SUVAT equations.
A relevant one is:
S = ut + 1/2 at^2

initital speed (u) is 0 as the case was dropped at no speed.

Therefore S = 1/2 at^2 for this case.
S= 0.5*9.8*(0.25^2)
S= 0.31m (2sf)
1
#3
ahhh thank you!
0
#4
(Original post by Stevo F)
You need to use the SUVAT equations.
A relevant one is:
S = ut + 1/2 at^2

initital speed (u) is 0 as the case was dropped at no speed.

Therefore S = 1/2 at^2 for this case.
S= 0.5*9.8*(0.25^2)
S= 0.31m (2sf)
ahhhhh thank you!
0
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