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GCSE Maths Help?
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texet
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An object will float in oil if its density is less than 0.7 g/cm^3
An object will float in water if its density is less than 1 g/cm^3
A spherical object has a radius of 0.38 meters.
Its mass is 200 kg.
Will the object float in oil or water?
Tick a box.
[ ] The object will float in oil and water.
[ ] The object will float in water but not in oil.
[ ] The object will not float in oil or water.
You must show your working out.
1000 kg/m^3 = 1 g/cm^3.
Volume of a sphere = 4/3 * pi * r^3.
[5 marks]
An object will float in water if its density is less than 1 g/cm^3
A spherical object has a radius of 0.38 meters.
Its mass is 200 kg.
Will the object float in oil or water?
Tick a box.
[ ] The object will float in oil and water.
[ ] The object will float in water but not in oil.
[ ] The object will not float in oil or water.
You must show your working out.
1000 kg/m^3 = 1 g/cm^3.
Volume of a sphere = 4/3 * pi * r^3.
[5 marks]
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RogerOxon
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#2
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#2
Please post your attempt.
The basic approach is to calculate the density of the object, from its mass divided by its volume (g/(cm)^3 is the most convenient here).
The basic approach is to calculate the density of the object, from its mass divided by its volume (g/(cm)^3 is the most convenient here).
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-Phoenix-
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#3
So you can work out the density of the sphere:
mass/volume
There are two ways to do this now:
1) Use kg/(m^3) and then divide by 1000 as they tell you
2) Convert kg & m into g & cm, and then work out the answer
Now, compare the density with the two given facts and you should have an answer
mass/volume
There are two ways to do this now:
1) Use kg/(m^3) and then divide by 1000 as they tell you
2) Convert kg & m into g & cm, and then work out the answer
Now, compare the density with the two given facts and you should have an answer
Spoiler:
Got B (Density 0.87g/cm^3)
Show
Got B (Density 0.87g/cm^3)
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username2980692
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#4
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#4
I got the density of the sphere as 0.870 (3sf) g/cm^3, which means that it will float in water but not in oil. Can't be asked to post my workings cause its too much writing lol 
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StudyJosh
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#5
To make it easier, convert the sphere's values to m and g
0.38 meters in cm = 38 cm
200kg in g = 200000g
Sphere volume
= 4/3 * pi * 38^3
= 219488/3 * pi
density = mass/volume
= 200000 / 219488/3 * pi
= 0.87... g/cm^3
The density is higher than 0.7 g/cm^3 so it will not float in oil but it is lower than 1 g/cm^3 so it will float in water.
0.38 meters in cm = 38 cm
200kg in g = 200000g
Sphere volume
= 4/3 * pi * 38^3
= 219488/3 * pi
density = mass/volume
= 200000 / 219488/3 * pi
= 0.87... g/cm^3
The density is higher than 0.7 g/cm^3 so it will not float in oil but it is lower than 1 g/cm^3 so it will float in water.
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