The correct answer is A. Solid Rock
The amount of heat required is B) 150 J
Explanation:
The amount of heat energy required to increase the temperature of a substance is given by the equation:

where:
m is the mass of the substance
C is the specific heat capacity of the substance
is the change in temperature of the substance
For the sample of copper in this problem, we have:
m = 25 g (mass)
C = 0.39 J/gºC (specific heat capacity of copper)
(change in temperature)
Substituting, we find:

So, the closest answer is B) 150 J.
Learn more about specific heat capacity:
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Answer:
Explanation:
Given
mass of tree stump is 
mass bullet is 
velocity of bullet is 
Conserving momentum for bullet and tree stump
Initial Momentum 
Suppose
is the velocity of the system
Final Momentum 
Initial momentum =Final Momentum


Answer: The coefficient of kinetic friction is μ = 0.6
Explanation:
For an object of mass M, the weight is:
W = M*g
where g is the gravitational acceleration: g = 9.8m/s^2
And the friction force between this object and the surface can be written as:
F = W*μ
where μ is the coefficient of friction (kinetic if the object is moving, and static if the object is not moving, usually the static coefficient is larger)
In this case, the weight is:
W = 20N
And the friction force is:
F = 12N
Replacing these values in the equation for the friction force we get:
12N = 20N*μ
(12N/20N) = μ = 0.6
The coefficient of kinetic friction is μ = 0.6