If pieces of equal size of woods, wax and iron falling from a same height, which one will reach the surface of the Earth first?

The movement of the Moon around the Earth is due to . . . . . . . .

A. Gravitational force

B. Centrifugal force

C. Concentric force

D. Nuclear force

Which one of the following statements about a satellite orbiting around the earth is correct?

A. Satellite is kept in orbit by remote control from ground station

B. Satellite is kept in orbit by retro-rocket and solar energy keeps it moving around the earth

C. Satellite requires energy from solar panels and solid fuels for orbiting

D. Satellite does not required any energy for orbiting

What will happen if an object is thrown into space with the speed of 8 km/s?

A. The object will go into space

B. It will return to Earth

C. It will rotate into the orbit of Earth

D. It will burst out

Astronauts feel . . . . . . . . weight inside the spacecraft.

A. more

B. less

C. zero

D. depends on G force