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When a stone thrown directly upwards reaches the top, it: A. Velocity and acceleration are zero. B. The velocity is zero and the acceleration is about 10 m/s2. C. Velocity is about 10 m/s and acceleration is zero. D. The velocity is about 10 m/s and the acceleration remains the same.

When a stone thrown directly upwards reaches the top, it: A. Velocity and acceleration are zero. B. The velocity is zero and the acceleration is about 10 m/s2. C. Velocity is about 10 m/s and acceleration is zero. D. The velocity is about 10 m/s and the acceleration remains the same. Correct Answer B

The correct answer is B.

  • When a stone thrown directly upwards reaches the top, its: Velocity is zero and the acceleration is about 10 m/s2.
  • This is true even when an object is thrown upward or has zero velocity.
  • The direction of velocity and acceleration for a ball thrown up in the air. At the highest point in its trajectory, the ball has zero velocity, and the magnitude of velocity increases again as the ball falls. The rock reaches the ground 10s after it is thrown.

Key Points

  • Speed is a scalar quantity. Velocity is a vector quantity and therefore can be negative, depending upon the coordinate system you use.
  • If in your coordinate system, Z is positive Upwards, then the speed of the stone (assuming that there is no air-induced drag) is 30 m/sec. However, the velocity of the stone would be 0, 0, -30 m/sec (X, Y, and Z portions of the velocity).

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