Question

a) If you release an object and there is no air resistance, it accelerates downwards by 9.8 m/s2. Instead, if you throw the object down, what is the downward acceleration after release?
  1. less than 9.8 m / s2.
  2. 9.8 m / s2.
  3. greater than 9.8 m / s2.

b) Explain what response option (1, 2 and 3) you would expect if there is any air resistance.

c) Explain which of the answer options 1, 2, or 3 you would expect if the object was thrown up

Answer 1

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Concept :

• The acceleration of the object is determined by the net external force acting on it.

$F_{net-external}=mass\times acceleration$

• The drag force on an object moving in a medium (air in this case) is opposite to the direction of the motion

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A)

In the case when there is no air resistance, the agents that are applying the force is "Earth's Gravitational pull" only. in the absence of air resistance, the velocity would NOT affect the force applied to it.

Hence the acceleration would be 9.8 m/s².

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b)

Since the object is thrown downwards, There is initially a velocity to it in the downwards direction. The body would experience a drag force in the direction opposite to the velocity. It would experience a drag force in the upward direction.

Hence the net force in the downward direction would be less than $mg$ .

Hence the acceleration would be less than 9.8 m/s².

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c)

In this case, the body has initially an upward velocity, so the drag force would be in the downward direction , Hence this would add to the net force in the downward direction.

Hence the acceleration would be greater than 9.8m/s²