## abdul_shabeer 3 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

Is it 2/0.5?

I am not sure.

3. abdul_shabeer

are you asking 2 or 0.5?

Is it 2 metre/second na?

5. abdul_shabeer

It's one of the option

which one? please do say the options.

7. abdul_shabeer

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

I think 2 * 0.5 = 1.

9. abdul_shabeer

Can you explain it?

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. gogind

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

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

13. salini

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

So even my answer is correct I believe.

15. salini

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

16. abdul_shabeer

Momentum is mass*velocity

But How?

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

19. abdul_shabeer

Key was not given

Oooooooooooooooo

21. salini

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

22. abdul_shabeer

This was given in FIITJEE

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

24. abdul_shabeer

In 8th?

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

26. gogind

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.

Yeah. so my answer is correct.

28. abdul_shabeer

What is dm/dt?

29. gogind

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

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

31. gogind

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.

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

33. gogind

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