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A projectile is moving upwards and rightwards towards the peak of its trajectory. Which one of the following force diagrams is representative of the FORCES acting upon the projectile during this portion of its flight?
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Definition of a Projectile:
A projectile is an object for which the only force acting upon it is gravity. The force of air resistance is negligibly small or nonexistent for a projectile.
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A force diagram is a diagram depicting all the forces acting upon an object. The forces are represented by arrows. Each individual force is represented by its own arrow directed in the direction of the force. There is only one force on a projectile - the force of gravity. Gravity pulls on an object in the downward direction. Thus, the only appropriate force diagram for a projectile is one which shows a single force, directed downwards.
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Many students confuse the direction that an object moves with the direction of the forces acting upon an object. In this question, it is common for such students to pick the diagram depicting an upward and rightward arrow due to the upward and rightward motion of the object. But don't be fooled! Such a diagram depicts the velocity vectors for a projectile, not the force vectors. While the object may be moving upward and rightward, the only force that acts upon it is the downward force of gravity.
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