Question

Haaalp. If a block of plastic is 0.6 as dense as water and weighs 100kg, what additional force will it take to poke it so that it is barely submerged

Answer 1

@ganeshie8 @Vincent-Lyon.Fr @Farcher

Answer 2

I can't figure out the equation

Answer 3

Overall mass must be that of the displaced water, that is the mass of the amount of water having the same volume as the block.

Answer 4

Think in terms of equilibrium

Answer 5

60kg

Answer 6

i think

Answer 7

cause it displaces the amount of weight of the submerged part

Answer 8

What is the volume of the block?

Answer 9

... dunno

Answer 10

it just gives me the weight

Answer 11

You are given mass and density of the block. Working out the volume is easy.

Answer 12

waaaait

Answer 13

demsity=mass/volume

Answer 14

so 0.6=100/x

Answer 15

so 166.666 repeating

Answer 16

i hope

Answer 17

Yep. What is the mass of that volume of water?

Answer 18

166.66?

Answer 19

cause 1.667*0.6 is 100

Answer 20

Yep, but please add units for volume and mass.

Answer 21

166.666 meters?

Answer 22

metre is a unit of length, neither volume nor mass

Answer 23

meter cubed

Answer 24

and 100 kg

Answer 25

No, it's liters here, or dm\(^3\)

For water (density 1) : 1 kg has a volume of 1 liter

Answer 26

oh

Answer 27

so 166.66 liters

Answer 28

Yes! Now, what is the corresponding mass of water?

Answer 29

whut do you mean

Answer 30

I mean What is the mass of water displaced by the block?

Answer 31

100 kg

Answer 32

??
The question states that the block is submerged in water.

Answer 33

cause of the principle of floatation

Answer 34

By the way, have you drawn a sketch of the situation?

Answer 35

yeah

Answer 36

not a very good one

Answer 37

There is no floatation here since there is an extra force pushing down on the block, in order to put it entirely under water.