题干

假设某伞兵做跳伞训练,他从悬停在空中的直升机上由静止跳下,跳离直升机一段时间后打开降落伞做减速下落.若他离地面约为100m时迅速打开降落伞,他打开降落伞后的速度图线如图甲所示,降落伞用8根对称的绳悬挂运动员,每根绳与中轴线的夹角均为37°,如图乙所示.已知人的质量为60kg,降落伞质量为10kg,不计打开降落伞前伞兵下落所受的阻力,打开伞后降落伞所受阻力Ff与速度v成正比,即Ff=kv,k为阻力系数,求(取g=10m/s2):


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    We eat in our cars, at our desks, on the go, and in front of the TV. We eat take-out, packaged and prepared meals. Why? Because it fits our not-enough-time-in-the-day lifestyles____ Well, I'm certainly not the first one to think it—or say it—but we all need to slow down.

    Consumer trends around the globe show that over the past three decades people are purchasing more prepared foods at the grocery and eating out more than ever before. It's predicted that we'll spend more at restaurants in the coming years____However, we're getting less healthy.

    While debates can be seen indifferent media over the food industry's contribution to our growing waistlines and our health problems, the bottom line is this____We can choose to eat a fast-food lunch on the go. We can throw a frozen meal in the microwave and call it dinner. We can eat without thinking, in front of the tube, at our computers, and while driving a car.

    ____Studies have shown meaningful links between family meals and kids' mental and physical well-being. Eating sensibly doesn't take much time or money, but it does require you to make a conscious decision to do so. Wrapped in endless work, appointments and social activities, we often fail to enjoy a relaxing meal with our families.

    While it can be a challenge to always put healthy eating first, just do your best. Remember that the food you eat has a more significant impact on your health, weight and well-being than almost any other activity you do.____ Every meal made at home—even just once or twice a week—is a step closer to a healthier body and as lower food lifestyle.

A. Our food matches our lives.

B. Treat it with the importance that it deserves, but start small.

C. We're consuming an increasing number of calories.

D. Lunch is the biggest calorie intake when it comes to eating out.

E. Purchase food locally and skip as many packaged items as you can.

F. What we eat, where we eat and how we eat are all under our control.

G. We can devote an hour of the day to enjoying a meal with our families.