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# Physics forces question query watch

1. A scale reads 0.4 mg
What is the force acting on the scale if the gravitational field strength is 9.8?

I calculated 3.92 * 10^-6 N
But apparently the anwer is 3.92 * 10^-3
I'm not sure if the answer is just wrong or I'm calculating it incorrectly

0.4 mg = 4 * 10^-7 kg
Mass in kg * gravitational field strength = force
Therefore
4 * 10^-6 * 9.8 = 3.92 * 10^-6 N
2. (Original post by AustinKingsley)
What is the force acting on the scale if the gravitational field strength is 9.8?

I calculated 3.92 * 10^-6 N
But apparently the anwer is 3.92 * 10^-3
I'm not sure if the answer is just wrong or I'm calculating it incorrectly

0.4 mg = 4 * 10^-7 kg
Mass in kg * gravitational field strength = force
Therefore
4 * 10^-6 * 9.8 = 3.92 * 10^-6 N
Take the mass in grams
3. (Original post by stoneroses2828)
Take the mass in grams
Why does it need to be grams?
4. (Original post by AustinKingsley)
Why does it need to be grams?
You've converted wrong. 1MILI gram is one thousandth of a kilogram. I.e. 1mg = 1*10^3 kg hence 0.4mg = 0.4*10^-3kg.

how do you convert 0.4mg to kg? I'm confused by your working.
5. (Original post by stoneroses2828)
Take the mass in grams
SI units for mass is kilograms bro
6. (Original post by BTAnonymous)
You've converted wrong. 1MILI gram is one thousandth of a kilogram. I.e. 1mg = 1*10^3 kg hence 0.4mg = 0.4*10^-3kg.

how do you convert 0.4mg to kg? I'm confused by your working.
Actually 0.4mg isnt 4*10^-4 kg. Its 4*10^-4g. So therefore 0.4mg = 4*10^-7kg
7. (Original post by Rhiaaaaa)
Actually 0.4mg isnt 4*10^-3 kg. Its 4*10^-3g. So therefore 0.4mg = 4*10^-6kg
I meant that, lol.
8. (Original post by AustinKingsley)
What is the force acting on the scale if the gravitational field strength is 9.8?

I calculated 3.92 * 10^-6 N
But apparently the anwer is 3.92 * 10^-3
I'm not sure if the answer is just wrong or I'm calculating it incorrectly

0.4 mg = 4 * 10^-7 kg
Mass in kg * gravitational field strength = force
Therefore
4 * 10^-6 * 9.8 = 3.92 * 10^-6 N
Answer is 4*10^-7 * 9.8 = 3.92*10^-6 N
9. (Original post by Rhiaaaaa)
Actually 0.4mg isnt 4*10^-4 kg. Its 4*10^-4g. So therefore 0.4mg = 4*10^-7kg
So the mark scheme must be wrong?

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