Escape Velocity Given Radius of 2 Objects

In summary, you forgot to convert the mass of the objects to kg, and also the answer for the neutron star is off by a lot.
  • #1
bigman8424
25
0
Got a dosie of a problem I need checked. I've been playing around with this problem, and after I submit the right answer (the ans. I got) , it came out wrong. Someone tell me what I'm doing wrong PLEASE thanks:

The prob. is to calculate escape velocity from a white dwarf and a neutron star. They are each 1 solar mass. The white dwarf has a radius of 104 km + the neutron star has a radius of 10 km.

Step I took:
sqr. root of 2GM/R = V = Sqroot of (2)(6.67e(-11)(1) all over 10^4th power
v = 1.15e(-7)

neutron star v= (2)(6.67e(-11)(1) all over 10
v = 3.65e(-6)
i got that, but only got half credit for this prob., what did I do wrong or have to add??
thanks
 
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  • #2
Looks like you forgot to convert the mass of the objects to kg. You put in "1" for both cases, but a solar mass is equal to 2e30 kg.

Also note that the escape velocity from a neutron star is near the speed of light, so the classical calculation you did won't be very accurate.
 
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  • #3
Converting to Kg

Oh I see so I did the prob. right, but just messed up on the conversions, so close. Just out of curiosity what the correct answer would be, is it going to be V = 1.15 e-10 and for the neutron star 3.65e-9

just trying to learn this, so i don't mess up next time

thanks a lot
 
  • #4
Whenever you get an answer, you should always go back and think if it makes sense. Would you expect it to take more or less speed to escape from a neutron star than, say, the earth? Does that check with the equation you used? Next, look at your answer. How fast is 10-10 m/s? Is it faster or slower than you can run? If you start running around, do you escape the Earth's gravity?
 
  • #5
you should also check your units! this will always helps.
 
Last edited:

1. What is escape velocity?

The escape velocity is the minimum speed that an object needs to escape the gravitational pull of another object.

2. How is escape velocity calculated?

Escape velocity is calculated using the formula: V = √(2GM/R), where G is the gravitational constant, M is the mass of the larger object, and R is the distance between the two objects.

3. Can escape velocity be calculated for any two objects?

Yes, escape velocity can be calculated for any two objects as long as their masses and distance between them are known.

4. How does the radius of the two objects affect the escape velocity?

The escape velocity is directly proportional to the radius of the larger object. This means that a larger radius will result in a higher escape velocity.

5. Is escape velocity the same for all objects?

No, escape velocity varies for different objects depending on their masses and distance between them. For example, the escape velocity for Earth is different from that of the Moon.

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