Final answer:
To calculate the values of g at Earth’s surface for the given changes in Earth’s properties, we can use the formula for gravitational acceleration. The value of g would be 4 times the original value if the mass is doubled and the radius is halved. The value of g would be the same as the original value if the mass density is doubled and the radius is unchanged. The value of g would be half the original value if the mass density is halved and the mass is unchanged.
Step-by-step explanation:
To calculate the values of g at Earth’s surface for the given changes in Earth’s properties, we can use the formula for gravitational acceleration given by:
 
g = G * (M/R^2)
 
Where G is the gravitational constant, M is the mass of the Earth, and R is its radius. Let's calculate the values for each scenario:
 
a) If the mass is doubled and the radius is halved:
 
Using the equation, we have:
 
g' = (2M)/(0.5R)^2 = 4g
 
So, the value of g would be 4 times the original value.
 
b) If the mass density is doubled and the radius is unchanged:
 
Using the equation, we have:
 
g' = G * (2M/R^2) = g
 
So, the value of g would be the same as the original value.
 
c) If the mass density is halved and the mass is unchanged:
 
Using the equation, we have:
 
g' = G * (M/R^2) = 0.5g
 
So, the value of g would be half the original value.