Question

求高人解决几道英文的物理题~

1.Assume maximal power output, how long in seconds would it take a 1335kg car with a 163 hp engine to accelerate from 54 km/h to 114 km/h?

2.A car with momentum 4875 kg m/s is travelling at a speed of 39 m/s. What is the car's weight?

3.A child in a boat throws a 235 g package horizontally out of the boat with a speed of 11 m/s. Calculate the speed of the boat immediately afterwards (in cm/s) assume it was initially at rest. The mass of the child is 46.1 kg and that of the boat is 95 kg.

4.Two cars leave the same point at the same time, each travelling at the same constant speed and each having the same mass. The first car drives directly east, while the second car heads directly north. If the centre of mass of the two-car system is travelling at 50 km/h ,how fast is each car travelling in km/h?

Answer 1

1、假设汽车处于最大功率163马力，质量1335千克，求从54km/h加速到114km/h需要几秒。
2、汽车动量4875kg*m/s,速度39m/s，求汽车重量。
3、一小孩从船上以11m/s水平抛出质量为235g的包，求船的速度,用cm/s。小孩质量46.1kg，船的质量95kg。
4、两辆车同时同地出发，速度大小相等，一个正东，一个正北，质心速度大小是50km/h,求车速，用km/h表达。
对于学过物理的来说都很简单，你自己解吧。

Answer 2

1、不知道163hp是什么东东，
大概意思：假定以最大输出功率，1个质量是1335kg的汽车从54km/h增速到114km/h，需要几分钟？该汽车的发动机是163hp。
2、动量P=4875，速度V=39m/s，质量M=P/V=4875/39=125kg.
3、物重m=235g=0.235kg，速度V1=11m/s；
人和船重M=46.1kg+95kg=141.1kg；
根据动量守恒：V2=m*V1/M=0.235kg*11m/s/141.1kg=0.01832m/s=1.832cm/s.
4、两车质心应该在东北方向，如果两车运动速度为V，那么质心运动速度为V/根号2，题目中给出了质心运动速度为50km/h，所以两车运动速度为50km/h*根号2=70.71km/h。