世勛 發問時間: 科學其他:科學 · 6 年前

物理 力和運動

1. If the mass M = 3.07 kg standard body has an acceleration 3.1 m/s^2 at 25.9 degrees to the positive direction of an x axis, what are (a) the x component and (b) the y component of the net force acting on the body, and (c) what is the net force in unit-vector notation? a_x + a_y

2. A certain particle has a weight of W = 35 N at a point where g = 9.8 m/s^2. At a point where G=4 m/s^2.What are its (a) weight (kgw) and (b) mass (kg)

3. An elevator cab that weighs 23 kN moves upward.

What is the tension in the cable if the cab's speed is increasing at a rate -2 m/s^2

4.A car that weighs 6700 N is initially moving 15 m/s when the brakes are applied and the car is brought to a stop in 27 m. Assuming the force that stops the car is constant, find (a) the magnitude of that force (F) and (b) the time required for the change in speed. (m/s)

5. Four penguins are being playfully pulled along very slippery (frictionless) ice by a curator. The masses of three penguins and the tension in two of the cords are m_1 = 5.5 kg,m_3 = 27.3 kg, m_4 = 36.1 kg,T_2 = 107.5 N, and T_4 = 244 N. Find the penguin mass m_2.

6. A 28 kg monkey climbs up a massless rope that runs over a frictionless tree limb and back down to a 7 kg package on the groun. (a) What is the magnitude of the least acceleration the monkey must have if it is to lift the package off the ground? If, after the package has been lifted, the monkey stops its climb and holds onto the rope, what are the (b) magnitude and (c) the tension in the rope?

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  • 6 年前
    最佳解答

    1. If the mass M = 3.07 kg standard body has an acceleration 3.1 m/s^2 at 25.9 degrees to the positive direction of an x axis, what are (a) the x component and (b) the y component of the net force acting on the body, and (c) what is the net force in unit-vector notation? a_x + a_y

    sol:

    by Newton's second law

    F = ma → F_x = ma_x = 3.07 × 3.1 cos25.9°

    F = ma → F_y = ma_y = 3.07 × 3.1 sin25.9°

    unit-vector = (3.07 × 3.1 cos25.9°) i + (3.07 × 3.1 sin25.9°) j

    參考資料: 蔡老師
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