Kinematics Question 633

Question: If retardation produced by air resistance of projectile is one-tenth of acceleration due to gravity, the time to reach maximum height

Options:

A) decreases by 11 percent

B) increases by 11 percent

C) decreases by 9 percent

D) increases by 9 percent

Show Answer

Answer:

Correct Answer: C

Solution:

[c] The time to reach the maximum height without air resistance;

$ t _{1}=\frac{u}{g}=\frac{u}{10} $ , and with air resistance, $ t _{2}=\frac{u}{10+1}=\frac{u}{11} $

$ =\frac{t _{1}-t _{2}}{t _{1}}\times 100=[ \frac{\frac{\text{u}}{\text{10}}-\frac{\text{u}}{\text{11}}}{\frac{\text{u}}{\text{10}}} ]\times 100 $

$ =9%( \text{decreases} ) $



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