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Physics 6
| Question | Answer |
|---|---|
| What is the formula for angle of rotation (angular displacement)? | Δθ = Δs/r (arc length divided by radius) |
| What are the SI units for angle of rotation, angular velocity, and angular acceleration? | Radians (rad), rad/s, rad/s² |
| How do you convert radians to degrees? | 1 rad = 180/π degrees |
| What is angular velocity? | Rate of change of angle of rotation |
| What is tangential velocity? | Instantaneous linear velocity of a rotating object |
| What is angular acceleration? | Rate of change of angular velocity |
| In rotational motion, what direction is positive vs. negative? | Counter-clockwise is positive; clockwise is negative |
| What is angular momentum? | Tendency of a rotating object to keep rotating |
| When is angular momentum conserved? | When the net external torque on a system is zero |
| What is moment of inertia? | Resistance to rotational motion |
| How does distance from the axis affect moment of inertia? | Greater distance (larger r) = greater rotational inertia = harder to change rotational velocity |
| What are the moment of inertia formulas for a hoop, solid cylinder, and solid sphere? | Hoop: I = MR²; Solid cylinder/disk: I = MR²/2; Solid sphere: I = 2MR²/5 |
| What is rotational kinetic energy | KE due to rotation |
| What is the work-energy theorem for rotational motion? | W = ΔKE_rot = ½Iωf² − ½Iωi² |
| What is Newton's Second Law in rotational form? | τ = Iα (torque equals rotational inertia times angular acceleration) |
| What is uniform circular motion? | Motion in a circle at constant speed; velocity direction constantly changes, creating centripetal acceleration |
| What is centripetal acceleration | Acceleration directed toward the center of the circle |
| How does centripetal acceleration change with speed and radius? | Increases with speed; increases as radius decreases |
| What is centripetal force | Any force causing circular motion, directed toward center |
| What is Newton's Universal Law of Gravitation? | F = GMm/r²; force is directly proportional to each mass and inversely proportional to distance squared |
| What is the difference between mass and weight? | Mass = amount of matter; weight = gravitational force on that mass (W = mg = GMm/r²) |
| What is the formula for gravitational acceleration (g) on any planet? | g = GM/r²; depends only on the planet's mass and distance from its center, not the object's mass |
| What is escape velocity and its formula? | Minimum speed to break free from a body's gravity; depends on the planet's mass and radius only — not the object's mass or initial velocity |
| A figure skater pulls their arms inward while spinning. What happens to their angular velocity and why? | Angular velocity increases. Pulling arms inward decreases moment of inertia (I). Since angular momentum L = Iω is conserved (no external torque), ω must increase to compensate. |
| Two objects orbit a planet — one at twice the orbital radius of the other. Which experiences greater centripetal acceleration, and why? | The inner object. Since ac = v²/r, a smaller radius produces greater centripetal acceleration at the same speed. Gravitational force also weakens with distance per F = GMm/r². |
| An object moves in uniform circular motion at constant speed. Is it accelerating? Explain. | Yes. Acceleration requires a change in velocity, and velocity is a vector with both magnitude and direction. Even at constant speed, the direction of velocity continuously changes, so centripetal acceleration exists pointing toward the center. |
| If you double the distance between two gravitationally attracting objects, what happens to the force? If you triple the distance? | Doubling distance reduces force to 1/4 of the original (since F ∝ 1/r²). Tripling distance reduces it to 1/9. The force decreases by the square of the factor by which distance increases. |
| A solid cylinder and a hoop have identical mass and radius. Which is harder to accelerate rotationally, and why? | The hoop (I = MR²) is harder than the cylinder (I = MR²/2). The hoop has all its mass concentrated at the outer edge, maximizing its moment of inertia, while the cylinder's mass is distributed closer to the axis, giving it lower rotational inertia. |
Created by:
smurtab