Answer:
We can use the work-energy principle to solve this problem. The principle states that the net work done on an object is equal to its change in kinetic energy. Assuming that the marshmallow is initially at rest, the net work done on the marshmallow by the person blowing into the pipe is equal to its kinetic energy after it leaves the pipe.
The net work done on the marshmallow is given by:
W_net = F_net * d
where F_net is the average net force exerted on the marshmallow, and d is the distance over which the force is applied. In this case, d is equal to the length of the pipe, which is 40 cm or 0.4 m. Substituting the given values, we get:
W_net = 0.7 N * 0.4 m
W_net = 0.28 J
The kinetic energy of the marshmallow after it leaves the pipe is given by:
K = (1/2) * m * v^2
where m is the mass of the marshmallow, and v is its speed. Substituting the given values, we get:
K = (1/2) * 0.0025 kg * v^2
K = 0.00000125 v^2 J
Equating the net work done on the marshmallow to its change in kinetic energy, we get:
W_net = K
0.28 = 0.00000125 v^2
Solving for v, we get:
v = √(0.28/0.00000125)
v = 16.73 m/s
Therefore, the speed of the marshmallow as it leaves the pipe is most nearly 16.73 m/s. However, this answer is not one of the options provided. The closest option is C) 15 m/s, which is a reasonable approximation given that the options are discrete and limited.