science help (1 Viewer)

d3st1nyLiang

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I don't quite get how to do these questions, thanks for any help

1. A ball is thrown vertically up in the air at an initial speed of 50m/s. Calculate

a) maximum height b) displacement at 3.5s c) time of flight

2. Shane Warne bowls a ball at 42m/s towards Sachin Tendulkar, who is then able to hit in the opposite direction at a speed of 50m/s. Calculate the change in momentum of the ball, if its mass is 500grams

hence, calculate the average force provided by the bat, if it is in contact with the ball for 0.1seconds

thanks
 

bored.of.u

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I don't quite get how to do these questions, thanks for any help

1. A ball is thrown vertically up in the air at an initial speed of 50m/s. Calculate

a) maximum height b) displacement at 3.5s c) time of flight

2. Shane Warne bowls a ball at 42m/s towards Sachin Tendulkar, who is then able to hit in the opposite direction at a speed of 50m/s. Calculate the change in momentum of the ball, if its mass is 500grams

hence, calculate the average force provided by the bat, if it is in contact with the ball for 0.1seconds

thanks
For 2:
change in momentum = m(v-u)
change in momentum = 0.5(42-(-50))
change in momentum = 46 Ns

Impulse = change in momentum = Ft
46 = F(0.1)
F = 460 N
 

aya-chan

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I don't quite get how to do these questions, thanks for any help

1. A ball is thrown vertically up in the air at an initial speed of 50m/s. Calculate

a) maximum height b) displacement at 3.5s c) time of flight

thanks
a) max height = displacement/2
where v = 0
u = 50 m/s
aand ... uhm. oh yeah. a = -9.8

and then sub that into ... the formula which I'm assuming you know.
I feel especially lazy today. :(
 

aya-chan

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v^2 = u^2 + 2as ... if you were wondering.

so ... 0 = 50^2 + 2 x -9.8 s

s = 127.551 ...

so max height = 63.776 ...

=D

well anyway, b) t = 3.5s ...
so use ...:
s = ut + ½ at

and you should get ...
s = 157.85

and then ... c) use v = u + at
where v = 0
u = 50m/s
a = -9.8

so ... t = 5.10...s
 

aya-chan

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well, you could make the initial 50 but then the other would be -42. It really just depends which direction you decide to be positive.

oh and you have to put the direction with it too. *forgot* so like
1a) 63.776 m up.
b) hey wait ... I just noticed... I must've done something wrong with the calculations somewhere.
c) is fine.

and 2. would be 460N towards Shane Warne
 

aya-chan

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There we go. that's what I left out. I left out the squared on the last t.
whoops.
 

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