The heat required to change the phase of a substance can be calculated by using the formula,
q = mCΔT where q is the heat needed, m is the mass of the substance, C is the specific heat capacity and ΔT is the change in temperature.
q = 7000 g (4.18 J/ g °C) (0°C - (-9°C))
q = 263340 J or .26334 MJ
Hope it's correct! ( If so rank as brainliest answer) :)
Answer: 1.95
Explanation:
You should start off from the decay formula and solve for τ:


Apply inverse logarithmic function:

The final form will be:

Inputing values for I, IO, and t:
Answer:
The gravitational force between these two objects is around 
Explanation:
The gravitational force can be written as:

Here:
- G is the gravitational constant

- m(1) is the first mass
- m(2) is the second mass
- r is the distance between two bodies.
If we see, the gravitational constant is a very small number, therefore the gravitational force is representative just when we have to massive bodies. Let's suppose that the mass of the pencil is 0.1 kg and the eraser is 0.1 kg too, the distance between them would be around 10 cm or 0.1 m, for instance.
Now let's calculate the gravitational force of these two bodies.
As we see it is very small force, so it is negligible relation to the earth gravitational force. That is why these two objects do not move towards each other.
I hope it helps you!
The phenomenon which is responsible for this effect is called diffraction.
Diffraction is the ability of a wave to propagate when it meets an obstacle or a slit. When the wave encounters the obstacle or the slit, it 'bends' around it and it continues propagate beyond it. A classical example of this phenomenon is when a sound wave propagates through a wall where there is a small aperture (as in the example of this problem)