Amount of watts needed to heat water

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To determine the power needed to heat water, it's essential to understand the relationship between calories and watts. A calorie is a unit of energy, while a watt measures power, which is energy per unit time. The conversion is approximately 0.239 calories per watt, but it's crucial to track units carefully to avoid confusion between seconds and hours. The small calorie (gram) definition should be used for accurate calculations. Understanding these conversions will help in calculating the required watts to heat the water effectively.
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I have a problem where I have a cup of water and I have to find out how much power I need to generate to heat it by a certian amount. I can't seem to find the equation I need in my book, can someone help me out? thanks.
 
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ok., now I am just trying to figure out how many watts = a calorie. is it 0.239 calories = 1 watt?
 
Keep in mind that a calorie is a unit of energy, and a watt is a unit of power. Do you know how to convert from power to energy? (hint -- keep track of your units so you don't mix seconds and hours, etc.)
 
i don't know, how do i convert watts to calories?
 
wakejosh said:
i don't know, how do i convert watts to calories?

It says how right at the top of the wikipedia page that I posted a link to. Use the small calorie (gram) definition.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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