Final answer:
The total energy of a 10-N object after free-falling 1 m is the sum of its potential and kinetic energy, which equals 40 J.
Step-by-step explanation:
The student's question involves calculating the total energy of a 10-N object after it has fallen 1 m in free fall from a height of 4 m above the ground. To find this, we need to calculate both the potential and kinetic energy at the point the object has free-fallen 1 m.
First, we find the remaining potential energy (PE) at 1 m above the starting point. Since PE is given by PE = mgh (where m is mass, g is acceleration due to gravity, and h is height), and the weight (W) of the object is the product of its mass (m) and gravity (g), i.e., W = mg, we can rewrite PE as W * h. With a weight of 10 N and a remaining height of 3 m (4 m - 1 m that it has fallen), the potential energy is 30 J (10 N * 3 m).
Since the object has fallen 1 m, it must have converted some potential energy into kinetic energy (KE). This kinetic energy can be calculated using KE = 1/2 m v^2, but since we are not given the velocity and we are dealing with conservation of energy, we can presume that the 10 J of potential energy lost (1 m fall * 10 N weight) is now kinetic energy. So at 1 m drop, the kinetic energy is 10 J.
The total energy of the object with respect to the ground at this point is the sum of its potential and kinetic energy, which is 30 J + 10 J = 40 J. Therefore, the correct answer is (b) 40 J.