Newton's Second Law for Translation and Rotation

BayRan · Oct 15, 2019

Answer choices: N2L for Translation, N2L for Rotation, Both, Either1. You are asked to find the angular acceleration of a low-friction pulley with a given force exerted on it.

My solution = N2L for rotation

Free-body diagram of a pulley of circle with a dot at its center, a rope wrapped over its right side, and a downward arrow labeled F with subscript YP.

2. You are asked to find the angular acceleration of a low-friction pulley due to a mass hanging from it by a rope.

My solution = Both

Diagram of a pulley hung from a horizontal ceiling line by a vertical string, with a rope running over the wheel and down to a square block at the bottom.

3. You are asked to determine the maximum height of a spinning ball that is thrown upwards.

My solution = Both

Diagram of a spinning baseball with an upward velocity arrow labeled v with a vector arrow above it, and a curved arrow below the ball showing its direction of rotation.

4. You are asked to calculate the time it takes a ball to roll down an inclined plane.

My solution = Both

Diagram of a circle resting on the upper edge of a sloped straight line that descends from left to right, touching it at one point.

5. You are asked to find the tangential acceleration of a small satellite in a circular orbit that results from it firing its thruster.

My solution = Both

Black-and-white diagram of Earth centred on Asia and Australia inside a large faint circle, with a small satellite on the outer circle at the right.

6. You are asked to determine the oribtal period of a small satellite around Earth.

My solution = N2L for translation

Black-and-white diagram of Earth centred on the Asia-Pacific region, showing Australia, Indonesia and East Asia, with a small satellite drawn on the orbit ring at the right edge.

Besides the first two, I'm really just guessing based on my intuition. Please help.

ZapperZ · Oct 15, 2019

Let's start with #3. You were asked to find the max height that the ball get to. Why should the fact that it is spinning matter? Did you have to include the spinning part when you solve such a problem? I'm assuming that this is elementary kinematics, and that you're not including Bernoulli effect due to the spinning ball moving through air.

Zz.

BayRan · Oct 15, 2019

ZapperZ said:

Let's start with #3. You were asked to find the max height that the ball get to. Why should the fact that it is spinning matter? Did you have to include the spinning part when you solve such a problem? I'm assuming that this is elementary kinematics, and that you're not including Bernoulli effect due to the spinning ball moving through air.

Zz.

That's true. I had always imagined that the ball would be spinning when someone throws it, but I assumed something would change when we apply N2LR. I changed my answer to N2L for translation.

Newton's Second Law for Translation and Rotation

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