Final answer:
The boy's force exertion in question 45 is false because the actual force depends on factors like ramp angle and friction. The voltage uniformity in a circuit diagram is also false due to voltage drops across components. Acceleration is proportional to the net external force, allowing for simplification when solving physics problems.
Step-by-step explanation:
The statement in question 45 that a boy pushing a 300 N box up a 1.0 m high and 3.0 m long ramp must have exerted a force of exactly 100 N is false. The work done on the box is equal to the force exerted along the ramp times the distance the box moves (assuming the force is constant and along the direction of the ramp). However, the actual force the boy needs to apply depends on various factors, such as the angle of the incline which determines the component of gravitational force working against him, and possible frictional forces on the ramp.
In the context of a circuit diagram, the statement that the voltage is the same at every point in a given wire is false. Voltage drops occur across components in a circuit, so the voltage is not the same at every point in the wire unless it is an ideal conductor with no resistance and no components between those points.
According to the second law of motion, acceleration (a) is directly proportional to the net external force (Fnet). This principle explains that internal forces, like the muscular forces within a child's body, can be ignored when calculating the net external force for easier problem-solving with minimal error.