题干

某次军事演习中,红方飞机甲正从北向南水平匀速飞行,飞行员发现其正前方距离x处有一架蓝方飞机乙正从东向西水平匀速飞行,随即水平发射炮弹,炮弹的发射方向与飞机的飞行方向成?角,经过时间t炮弹击中飞机乙。已知飞机甲的速度为v1,乙的速度为v2,甲在地面上静止时发射炮弹的速度为v0。忽略炮弹竖直方向的位移和所受的空气阻力。则下列说法中正确的是

A:

B:

C:

D:

上一题 下一题 0.0难度 选择题 更新时间:2012-11-19 08:23:17

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C

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    If you've been diagnosed with high blood pressure, you might be worried about taking medication to bring your numbers down. Chronic(慢性的) stress may contribute to high blood pressure. More research is needed to determine the effects of chronic stress on blood pressure. Occasional stress also can contribute to high blood pressure if you react to stress by eating unhealthy food, drinking alcohol or smoking.

    Take some time to think about what causes you to feel stressed, such as work, family, finances or illness. Once you know what's causing your stress, consider how you can rid or reduce stress. If you can't rid all of your stressors, you can at least handle them in a healthier way. Try to:

    Change your expectations. For example, plan your day and focus on your strengths. Avoid trying to do too much and learn to say no. Understand there are some things you can't change or control, but you can focus on how you react to them.

    Focus on issues you can control and make plans to solve them. If you are having an issue at work, try talking to your manager. If you are having a conflict with your kids or spouse, take steps to resolve it.

    Avoid stress triggers(诱因). Try to avoid triggers when you can. For example, if rush-hour traffic on the way to work causes stress, try leaving earlier in the morning, or take public transportation. Avoid people who cause you stress if possible.

    Make time to relax and to do activities you enjoy. Take time each day to sit quietly and breathe deeply. Make time for enjoyable activities or hobbies in your schedule, such as taking a walk, cooking or volunteering.

    Practice gratitude. Expressing gratitude to others can help reduce your stress.

    If you successfully control your blood pressure with reducing stress, you might avoid, delay or reduce the need for medication.