Motion Under Gravity
Easyphysics
A ball is thrown vertically upward with a velocity of 20 m/s. What will be its velocity when it returns to the point of projection? (g = 10 m/s²)
Select the correct option:
Solution
Incorrect! Answer:
-20 m/s
- Symmetry of Motion: For an object thrown upward under gravity (ignoring air friction), the time to rise equals the time to fall, and the speed at any level is the same during ascent and descent.
- Energy Logic: By conservation of mechanical energy, the kinetic energy at the point of projection must be recovered when it returns to the same height.
- Calculation:
- Speed at return = Initial Speed = 20 m/s.
- Direction Aspect: Initial velocity was upward (+20 m/s). Upon return, the ball is moving downward.
- Final Velocity: −20 m/s (using sign convention where up is positive).
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About This Question
- Subject
- physics
- Chapter
- kinematics
- Topic
- motion under gravity
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
-20 m/s
- Symmetry of Motion: For an object thrown upward under gravity (ignoring air friction), the time to rise equals the time to fall, and the speed at any level is the same during ascent and descent.
- Energy Logic: By conservation of mechanical energy, the kinetic energy at the point of projection must be recovered when it returns to the same height.
- Calculation:
- Speed at return = Initial Speed = 20 m/s.
- Direction Aspect: Initial velocity was upward (+20 m/s). Upon return, the ball is moving downward.
- Final Velocity: −20 m/s (using sign convention where up is positive).
This easy difficulty physics question is from the chapter kinematics, covering the topic of motion under gravity. It appeared in the 2025 exam.
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