# Homework Help: NSO class 9th

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1. Oct 21, 2015

### faiziqb12

• Warning: Homework template must be used and some solution attempt made.
A problem came in the previous years Olympiad ::

if we go inside a mine and drop 10 lb iron ball and 1 lb allumunium ball from top of a high platform, then
1. both will reach the ground at same time
2. 1 lb weight will reach the floor first
3. 10 lb weight will reach the floor first
4. incomplete data

but due to air resistance 10lb must have had fallen first..

2. Oct 21, 2015

### Borg

The difference in air resistance between the two spheres is neglible.

3. Oct 21, 2015

### faiziqb12

but accordi
but force of friction must vary with diffrent mass
won't it

4. Oct 21, 2015

### Borg

Air resistance is dependant on surface area. Again, the difference is going to be negilible.

5. Oct 21, 2015

### faiziqb12

then can you please answer why a sheet of paper and a lead sheet of the same surface area experience different air resistance forces

6. Oct 21, 2015

### Staff: Mentor

We won't do your work for you. You need to make some investigative effort here.

Choose representative masses for two objects. Assume that air resistance is identical for each, maybe call it fair. Draw Free Body Diagrams for both. Determine expressions for the accelerations. How do the accelerations compare?