1. Aug 31, 2010

### Danny523

Hi

I am going slightly insane with this question I have!!!

"A neutron contains two down quarks at a separation of approximately 10^−15 m. Calculate the strength in newtons of the electrical force between two down quarks at a separation of 1.0 × 10^-15 m."

Now I have used F= k x (Q1 x Q2 / r (squared))

so....

F = 9 x 10^9 x ((1/3) x (-1.6 x 10^-19 C))(squared) / (1.0 x 10^-15 m )(squared)

and I get 25.6 N

Im pretty sure this is wrong, Im sure its much higher than that.

Could anybody tell me where I am going wrong please.

Thanks

Danny

2. Aug 31, 2010

### Andrew Mason

I agree with your answer. Why do you think it should be much higher? We are talking about something with an extremely small mass, so this force is really enormous.

AM

3. Aug 31, 2010

### Danny523

I am questioning my answer because the next question of my assignment says this....

"Book 7 page 121 states that the strong force between two quarks ‘is equivalent to the weight of a 10-tonne truck’. Calculate the weight of a 10-tonne truck and compare this weight with the electrostatic force between the two down quarks in a neutron"

Ive seen example questions which come out with an answer much much larger, but the examples didnt show working. Im really confused. Im pretty sure my figures are right, just not the answer. I am confuuuuused!

4. Aug 31, 2010

### Andrew Mason

You were asked to find the electrostatic force between two quarks, not the nuclear force. The nuclear force between two quarks is much, much stronger. It is the nuclear force may be equivalent to the weight of a ten tonne truck.

Furthermore, since the two down quarks have the same charge (-1/3 e) the force between them is repulsive, so it works against the nuclear force between them (which, like gravity, is attractive).

AM

5. Sep 1, 2010

### Danny523

Ahhhhh ok, I think it has just become clearer to me now!!!!

Thank you so much!

Danny

6. Aug 9, 2012