在光滑水平面上有一辆平板车，质量分别为m1、m2的两人站在车的两端（如图所示），他们以对地速度v1、v2相向而行，则在下 * * 情况下，车的运动方向如何？
（1）m1=m2,v1=v2;
(2)m1≠m2,v1=v2;
(3)m1=m2,v1≠v2.
（1）平板车不动.
（2）m2>m1时，平板车向右运动；
m2<m1时，平板车向左运动.
（3）v2>v1时，平板车向右运动；
v2<v1时，平板车向左运动.
以m1、m2和车为系统，规定v1方向为正方向、设车质量为M.由动量守恒，得
m1v1-m2v2+Mv=0
(1)当m1=m2、v1=v2时，得v=0，所以平板车不动.
（2）当v1=v2、m2>m1时，得v>0,所以平板车向右运动；
当v1=v2、m2<m1时，得v<0，所以平板车向左运动.
（3）当m1=m2、v2>v1时，得v>0，所以平板车向右运动；
当m1=m2、v2<v1时，得v<0,所以平板车向左运动.
| Awarded the Nobel Prize for physics in 1918, German physicist Max Planck is best remembered as the originator of the quantum theory. His work helped usher in a new era in theoretical physics and revolutionized the scientific community’s understanding of atomic and subatomic processes. Planck introduced an idea that led to the quantum theory, which became the foundation of twentieth century physics. In December 1900, Planck worked out an equation that described the distribution of radiation accurately over the range of low to high frequencies. He had developed a theory which depended on a model of matter that seemed very strange at the time. The model required the emission of electromagnetic radiation in small chunks or particles. These particles were later called quantums. The energy associated with each quantum is measured by multiplying the frequency of the radiation, v, by a universal constant, h. Thus, energy, or E, equals hv. The constant, h, is known as Planck’s constant. It is now recognized as one of the fundamental constants of the world. Planck announced his findings in 1900, but it was years before the full consequences of his revolutionary quantum theory were recognized. Throughout his life, Planck made significant contributions to optics, thermodynamics and statistical mechanics, physical chemistry, among other fields. |
It can be inferred from the passage that Planck’s work led to the development of which of the following
A．The rocket.
B．The atomic bomb.
C．The internal combustion engine.
D．The computer.