Motion Under Gravity - NEET Physics Questions
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Motion Under Gravity

Question 1:

A particle is thrown upwards from ground. It experience a constant air resistance force which can produce a retardation of 2 m/s². The ratio of time of ascent to the time of descent is : [g = 10 m/s²]

1. 1 : 1
2. \[\sqrt{\frac{2}{3}}\]
3. 2/3
4. \[\sqrt{\frac{3}{2}}\]
View Answer

Effective accelerations:
- Ascent: \( a_{\text{eff}} = g + a = 10 + 2 = 12 \, \text{m/s}^2 \)
- Descent: \( a'_{\text{eff}} = g - a = 10 - 2 = 8 \, \text{m/s}^2 \)

Ratio of times:
\[
\frac{t_a}{t_d} = \sqrt{\frac{a'_{\text{eff}}}{a_{\text{eff}}}} = \sqrt{\frac{8}{12}} = \sqrt{\frac{2}{3}}
\]

The ratio of time of ascent to time of descent is √(2/3).

Question 2:

A body dropped from the top of a tower clears 7/16th of the total height of the tower in its last second of flight. The time taken by the body to reach the ground is :

1. 2 s
2. 3 s
3. 4 s
4. 5 s
View Answer

According to Galileo's Ratio of Odd Number distances travelled is consecution interval of 1 sec is in the ratio of 1:3:5:7 so in 4th second distance travelled is 7/16th of total journey.

so, total time = 4 sec.