Cranberries are a tart berry grown in the New England region of the United States. Fresh, high quality berries are fairly hard whereas rotten berries are squishy. To help sort the good berries from the bad, farmers developed a bounce board separator, in which the cranberries are dropped from a fixed height. Good ones bounce, rotten ones don't, and the machine is configured such that there is a wall the berries must bounce over to qualify as fresh. You can see a video of such a machine in operation here .
A rotten cranberry will lose at least 9 0 % of its total energy during a bounce. If the cranberries are dropped from a height of 1 0 cm , what is the minimum height in cm of the wall so that no rotten cranberries could ever bounce over it?
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Hahaha what a joke this problem LOL
Easy just use EP= m.g.h M and G = K 10-90%= 1
As the berries are dropped from 1 0 c m height, the good berries will surely bounce over 1 0 c m height... It's given that the rotten berries loss 90% of it's energy... So, it'll not bounce over,
90% of 1 0 c m = 1 0 c m × 1 0 0 9 0 = 1 c m
Hence, the required answer is 1 ...
By the mechanic energy conservation principle, when the object falls, all potencial energy becomes kinetic energy. However, the object loses 90% of its total energy, so we can conservate the energy from the bouncing instant to the moment it reaches the highest height:
0.1(mgH)=mgh ---> 0.1(10^-1)=h ----> h= 1cm.
Potential energy after bouncing will be 0.1 of mgh = mg (0.1)h The height to which they rise is 0.1 10 = 1 cm is the answer.
The cranberry has some gravitational potential energy when it is released. After bouncing, at its new highest point it will have 90% less gravitational potential energy: although some energy was converted to kinetic and back, conservation of energy tells us that none got 'lost' apart from the 90% specified.
For distances that are small relative to the size of the earth, gravitational potential can be approximated by (mass * height * acceleration due to gravity). So losing 90% of its energy means that it loses 90% of its bounce height (mass and gravity are constants).
A rotten cranberry will lose 90% of its energy, so only 10% energy will be left. Energy is directly proportional to the height, which means that 10% energy left will result in only 10% of height reached. Thus, 10% of 10 cm is 1cm
(M V^2)/2=10 (MgH/100) cause 90% was lost during the fall.
so V^2=2g ,by the conservation of energy : mgh=(mV^2)/2 , h=2g/2g=1
By the Law of Conservation of energy applied on the cranberries, we can write Ep = mgh and Ek = Ep , and after they bounce they lose 90 % of their energy. So their energy is 0,1 * Ep = mgx, where x is the minimum height of the wall. 0,1*mgh = mgx => x = 0,1 h = 0,1 * 10cm = 1 cm.
Let the energy at the initial point of drop be = E
As the energy is only with respect to its height , E = m g H (where m is mass of the object g is the acceleration due to gravity & H is the height from ground)
Now as the berry hits the ground and bounces back it loses energy as given n now let energy = E_(2)
e = m g h (h is the new height) Given e = 0.1 E => m g h=0.1 * m g*H
h = 0.1 * 10 = 1 cm
A rotten cranberry loses at least 9 0 % of its energy during a bounce, so it retains no more than 1 0 % of its energy. This means that the cranberry will only bounce at most 1 0 % as high as it was dropped from, so if it is dropped from 1 0 cm, it can only bounce up to 1 0 ⋅ 1 0 % = 1 cm high. Thus, the minimum wall height is 1 cm.
The height of the wall must be at least the height of the rotten cranberries that bounce highest, so the height of the wall is the height a cranberry which loses 9 0 % of its energy will bounce to. The potential energy of the cranberry is proportional to its height. Therefore, if it is dropped from 1 0 cm and it loses 9 0 % of its energy, it only has the energy left to reach 1 0 % of its initial height, which is 1 0 ⋅ 0 . 1 = 1 cm.
We can use the ratio principle to do this problem.
We know that the cranberries are dropped from h = 10 cm
If the cranberries are lost at least 90 % of it's energy.... So that's mean that, the cranberries only have 10 % of it's initial energy to bounce.
So, the minimum height in cm of the wall so that no rotten cranberries could ever bounce over it is : 10 % x h = 10 % x 10 cm = 1 cm
mgh/mgh'=100/10 so,h'=h/10=(10/10)cm=1 cm
Since 90% of the energy is lost, 10% of the energy is conserved. Therefore, mgh = (1/10)mgh . By cancelling out the mg, we know that the minimum height that the cranberry can bounce is 1/10 of the original height which is 1/10(10) = 1cm.
As a rotten cranberry will lose 90% of its energy during a bounce,then the minimum height of the wall is 1 − 1 0 9 × 1 0 c m = 1 0 1 × 1 0 c m = 1 c m
Energy in it = mg10
only 100-90 = 10% energy it will left
so only 10% of 10 cm = 1 cm will be the height
After the bounce, the rotten cranberry loses at least 90% of its energy, and so it can only have at most 10% left. Ten percent of 10 cm is one centimeter. Explanations aside, that's about it.
Potential energy = mass x gravity x height
Since 90 % of energy is lost, 10% is conserved.
10/100 x m x g x 10 cm( before bounce)= m x g x h ( after bounce) Therefore, h= 10/100 x 10 = 1 cm
Seeing that a tenth of energy is consumed, (1/10)(10cm)=1cm
When a berry is dropped from a height h1 total energy of the berry is mgh1.
90% of this energy is lost in one bounce, therefore energy remaining=0.1mgh1.
After bouncing if the berry rises to a height h2 then total energy of the berry is mgh2. According to conservation of energy,
mgh2=0.1mgh1
i.e h2=0.1h1
Plug in the value and get the answer.
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We must assume the case where the rotten cranberry loses 90% of its total energy. Dropping from a height of 10 centimeters, it can only bounce up to 1 cm, which is our answer.