bc 發問於 科學及數學其他 - 科學 · 1 十年前

2 questions about acids and force

1. A test is carried out to compare the strengths of 3 types of acids : citric, ethanoic and hydrochloric. Zinc podwer is used. Why it is powder but not ribbon? Also, List 3 conditions to be kept the same for a fair test.

2. Why the landing craft does not need to use a parachute to land on the moon?


one more question

3. If the bulbs are rated at '200V,50W',what is the current flowing through ? Show calculation.

更新 2:

amendment on question 3

3. If the bulbs are rated 200V, 50W then what is the current flowing through? show calculation.

2 個解答

  • 1 十年前

    1. To determine the strengths of the three types of the acids: citric acid, ethanoic acid and hydrochloric acid, zinc powder is used instead of ribbon because:

    → This can increase the surface area for the reaction between the acids and zinc, this may make the observation more obvious.

    2. The principle of parachute is to increase the surface area with the air, then air resistance (acting in the direction opposite to the direction of falling) can be increase drastically and hence the parachutist will not free fall and can fall in an uniform velocity, this is safer for landing.

    However, atmosphere is absent in the Moon. So there is no air resistance for landing. Even the parachute is opened, the landing craft will still experience an acceleration due to gravity.

    Therefore, parachute is not needed for the landing craft on the Moon.

    3. Let the current flow be I

    Voltage supplied, V = 200 V

    Power of the bulb, P = 50 W

    By the equation, P = IV

    50 = I(220)

    Current, I = 0.227 A

    資料來源: Myself~~~
  • choy
    Lv 5
    1 十年前

    1. To increase the surface area for reactions to take place.

    Temperature, concentration, quantity of zinc

    2. Moon has no atmosphere. Even if a parachute is used, it will not experience any air resistance.