Question

英文物理题,麻烦英文高手们帮忙~谢谢~

1.Today I drove 125 miles in 110 minutes. What was my` average speed in miles per hour?(There are 60 minutes in one hour)
(能不能帮我列出完整的式子)

2.Light travels through space at a constant speed of 3X10⁸m/s. What is the acceleration of a beam of light?

3.what is the acceleration of a car if it begins at 100km/h and comes to a stop after 8 seconds? you may write your answer with the units of km/h/s. In what direction is the car's acceleration (in the same direction or opposite direction of the car's motion)?

希望可以讲得详细一些,很急用!!
谢谢了~

Answer 1

1、Today I drove 125 miles in 110 minutes. What was my` average speed in miles per hour?(There are 60 minutes in one hour)

Ans：average speed v=total course/time cost=125/(110/60)≈68.18 miles/hour

2、Light travels through space at a constant speed of 3X10⁸m/s. What is the acceleration of a beam of light?

Ans：Since the speed of a beam of light is a constant, the acceleration is zero(0).

3、what is the acceleration of a car if it begins at 100km/h and comes to a stop after 8 seconds? you may write your answer with the units of km/h/s. In what direction is the car's acceleration (in the same direction or opposite direction of the car's motion)?

Ans: the acceleration a=(0-100)/8=-12.5km/h/s
where "-" suggests that the acceleration is opposite the direction of the car's motion.

Answer 2

1:
Conversion of Time: 110 Minutes = 110/60 = 11/6Hours
Average Speed = 125Miles/11/6Hours =68 Miles per Hour.
(This is not a physical question)

2: The acceleration is Zero for the speed of Light is constant and stable, there is no speed variation.

3: As the question told you, you can use the unit of km/h/s, That means you can use the speed variation and the time directly without a conversion:
The acceleration = (0km/h - 100km/h) / 8 seconds = -12.5km/h/s and this result means that the acceleration is not in the same direction in which the car is heading.

Over.