anonymous 4 years ago Gravel is dropped on a conveyor belt at the rate of 0.5kg/s. The extra force in Newton required to keep the belt moving at 2m/s, is

1. anonymous

Is it 2/0.5?

2. anonymous

I am not sure.

3. anonymous

are you asking 2 or 0.5?

4. anonymous

Is it 2 metre/second na?

5. anonymous

It's one of the option

6. anonymous

which one? please do say the options.

7. anonymous

(a) 1N (b) 2N (c) 4N (d) 0.5 N

8. anonymous

I think 2 * 0.5 = 1.

9. anonymous

Can you explain it?

10. anonymous

What I think is the conveyor belt is initially at rest. Gravel mass is 0.5 kg. Now given velocity is 2 m / s. So just multiplied using the force formula.

11. anonymous

It is, but you need a reason behind it :D

12. anonymous

I request others to check and criticize me if I am wrong.

13. anonymous

force=momentum*time so momentum is given for unit time (1 second) determine it

14. anonymous

So even my answer is correct I believe.

15. anonymous

the force is nevertheless 0.5N no matter how u speed up

16. anonymous

Momentum is mass*velocity

17. anonymous

But How?

18. anonymous

Abdul, What is the correct option given in the key?

19. anonymous

Key was not given

20. anonymous

Oooooooooooooooo

21. anonymous

sry i dint read the question properly so yes first find momentum and then force

22. anonymous

This was given in FIITJEE

23. anonymous

I could know that. U can even find such questions in BMA workbook.

24. anonymous

In 8th?

25. anonymous

Yeah. Its actually 9th portion. Still u can try.

26. anonymous

Write the net force as: $\ F_{net}= F - F_{thrust}$ it is -F_thurst because the mass in increasing The net force is zero because the system is not increasing or decreasing its velocity, that is the velocity is constant. Now, $\ F_{thrust}=v\frac{dm}{dt}$ I think it is fairly easy to solve it now :D.

27. anonymous

Yeah. so my answer is correct.

28. anonymous

What is dm/dt?

29. anonymous

change in mass per unit time or how much mass is added per second.

30. anonymous

Even I will know the use of "d" in formulae in 11th grade. Can anyone explain it in detail?

31. anonymous

d is a symbol for a differential. It represents an infitesimal change of some quantity (you will get to that in calculus). It's like $\ \Delta$ but infinitely small.

32. anonymous

So, its a very tough concept. What about Calculus? I just know 2 words - Integration and Differentiation.

33. anonymous

Yes that's what you do in Calculus :D. If you are impatient to learn about it I would recommend "Calculus" by Gilbert Strang Link: http://ocw.mit.edu/ans7870/resources/Strang/Edited/Calculus/Calculus.pdf