Question

Noting the large stresses that can be caused by thermal expansion, an amateur weapon inventor decides to use it to make a new kind of gun. He plans to jam a bullet against an aluminum rod inside a closed invar tube. When he heats the tube, the rod will expand more than the tube and a very strong force will build up. Then, by a method yet to be determined, he will open the tube in a split second and let the force of the rod launch the bullet at very high speed. What is he overlooking?

a) Invar tube will expand more than the aluminum rod.
b) The aluminum rod will not generate enough force.
c) The invar tube will also expand, reducing the force.
d) Thermal expansion cannot be harnessed for this purpose.

Answer 1

The inventor is overlooking the fact that the Invar tube will also expand when heated, reducing the force that could be used to launch a bullet. Invar has a low expansion coefficient, so its expansion may make the force generated by the aluminum rod insufficient for the intended purpose.

Step-by-step explanation:

The amateur weapon inventor's plan of using thermal expansion to launch a bullet is overlooking the fact that the Invar tube will also expand, reducing the force. Invar has a very low thermal expansion coefficient, which means it expands very little when heated compared to most metals. However, even a small amount of expansion can relieve some of the stress that would otherwise build up due to the expansion of the aluminum rod. This can make the force generated by the rod insufficient to launch the bullet at a very high speed. Furthermore, the complexities of evenly heating the materials and the method of opening the tube rapidly without losing too much energy also present significant practical challenges.

Answer 2

The inventor is overlooking the fact that the Invar tube will also expand when heated, reducing the force that could be used to launch a bullet. Invar has a low expansion coefficient, so its expansion may make the force generated by the aluminum rod insufficient for the intended purpose.

Step-by-step explanation:

The amateur weapon inventor's plan of using thermal expansion to launch a bullet is overlooking the fact that the Invar tube will also expand, reducing the force. Invar has a very low thermal expansion coefficient, which means it expands very little when heated compared to most metals. However, even a small amount of expansion can relieve some of the stress that would otherwise build up due to the expansion of the aluminum rod. This can make the force generated by the rod insufficient to launch the bullet at a very high speed. Furthermore, the complexities of evenly heating the materials and the method of opening the tube rapidly without losing too much energy also present significant practical challenges.