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} ) $
