University physics答案2023秋

第五章测试

1.For an isolated system, the total momentum of the system is conserved when the vector sum of the external forces is zero. （ ）
A:对 B:错
答案:A
2.An object with a mass of 15kg is placed on the bottom plate of a crane. If the bottom plate of the crane accelerates up and the acceleration is . Given , the impulse of the object given by the bottom plate of the crane within 2 seconds is （ ）.
A:360kgm/s B:400kgm/s C:300kgm/s D:180kgm/s 3.when the impulse is constant, the longer the action time, the smaller the impulse. （ ）
A:对 B:错 4.An object with a mass of 2kg is thrown upward at the speed of 10m/s with an inclination angle of 30º, the magnitude of impulse received by the object when it moves to the highest point is （ ）.
A:20kgm/s B:36kgm/s C:10kgm/s D:30kgm/s 5.A static object burst into three pieces, two of which have the same mass, and the same speed of 20m/s with the direction of perpendicular to each other. The mass of the third piece is exactly equal to the sum of the other two pieces, then the speed of the third piece is （ ）.
A: B: C: D: