describe escape velocity of a rocket.?

Answer 1

It's more or less as most of the preceding answers say. But it applies to escape from any body, not just earth and not just planets. For instance, the sun also has an associated escape velocity (617.2 km/sec at the surface). And it applies to a launch in any direction away from the body, not only vertical. As the 4th answer says, escape velocity decreases with distance from the body. Interestingly, because of conservation of energy, the velocity of an object launched at escape velocity remains equal to the escape velocity that prevails at whatever distance it reaches.
A rocket achieves escape velocity by expelling the exhaust of its burning propellant rearwards at high velocity. It is most practically done by launching along a path that is initially vertical to minimize time spent in the dense atmosphere and consequent energy loss to air resistance, and then gradually changing to a more horizontal path to minimize the loss due to gravitational acceleration. Ignoring these loss factors, the velocity of a rocket is described by the "rocket equation",
DeltaV = Vex * log(M0/M1),
Where DeltaV is velocity change, Vex is exhaust velocity, M0 is liftoff mass and M1 is burnout mass.

Answer 2

The escape velocity can be calculated easily for any planet, moon, or other object by conservation of energy and using elementary calculus. Consider the earth's gravitational field (or any other gravitational field) as a "well" that has negative potential energy that must be overcome to get free.

The equation for the gravitational force is F= G m1 m2 /r^2

where m1 is the mass of the rocket, m2 is the mass of earth (or other planet, moon, etc.) G is the gravitational constant, and r is the separation of the two centers of gravity.

Integrating this equation from r= r0 to infinity gives your equation for work that must be done to overcome the force of gravity.

Then, use conservation of energy: kinetic energy of rocket (= 1/2 m1 v^2) where v is your escape velocity + gravitational potential energy (negative - remember, we are in a gravitational well) = 0.

At infinity, there would be no gravitational attraction and the rocket would have no kinetic energy if it left the earth (or other object) at the escape velocity.

Answer 3

Escape velocity is the initial velocity required by a projectile to rise vertically and just escape the gravitational field of a planet.

Answer 4

The rocket blasts off vertically, and can't possibly reach 7 miles a second. As it rises, its track begins to curve becoming more horizontal to the earth, but still gaining altitude. As it gets closer to the boundry of space, there is less friction, and so the rocket can reach 7 miles a second, and escape earth's gravity.

Answer 5

Escape velocity is the velocity of any object to escape from the earth, that is it will not return to earth again.
It is 11.2 km/s on the surface of earth. It decreases as the distance from the surface is increased.

Answer 6

If memory serves me correctly the escape velocity of a rocket is 70 ft/sec/sec. To learn the exact answer please refer to Isaac Asimov's Book Of 3,000 facts

Answer 7

7 miles per scond. At that speed, the effects of gravity will decrease slightly more rapidly than the rocket slows down, meaning it will never fall back to earth.

Answer 8

7.8 m/s