A 65-kg astronaut is in the space shuttle in orbit around the Earth. A) The astr

Question

A 65-kg astronaut is in the space shuttle in orbit around the Earth.

A) The astronaut feels weightless. Is it correct to say that the force of gravity acting on her is zero? Explain your answer.

B) Why doesn't the shuttle simply crash into the Earth?

C) The astronaut lands on an airless planet that has the same mass as the Earth but is the size of the moon. How would her weight on this planet compare to her weight on Earth - more, less, or the same? Explain.

D) While on this planet, the astronaut practices hitting some golf balls. She hits one at an angle 20 degrees above the horizon, and another at an angle of 70 degrees above the horizon. Which ball lands further away from her? Which is in flight longer? (hint the laws of physics are the same on this planet as on Earth).

E) The astronaut rolls two of the golf balls off a flat table, one with a speed of 3 m/s and the other with a speed of 5 m/s. The balls leave the table at the same instant. Which ball hits the ground first (ignore air resistance). Explain.

Explanation / Answer

a] It is wrong to say that the force of gravity is zero. The net force on her is zero.

b] The gravitational force due to earth provides the necessary centripetal force for the shuttle to revolve around earth.

c] Since the planet is of the size of the moon, the gravitational force will be lesser than that on earth and hence her weight will be lighter there.

d] R = u2sin(2 x theta)/g'

=> sin(2 x 20) = sin(2 x 70)

therefore, both the balls will land at the same place.

T = 2usin(theta)/g'

The time of flight will thus be more for 70o. [since sin70 > sin20]

E] H = uyt - (1/2)g' t2

=> H = 0 - (1/2)g' t2

this does not depend on the velocity.

so, both the balls will hit the ground at the same time. The horizontal distance covered by both, however, will be different.

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