जब कोई पिंड गुरुत्वाकर्षण के अंतर्गत स्वतंत्र रूप से गिरता है, तो निम्नलिखित में से कौन सी राशि नियत नहीं रहती है?

On Earth, g ≈ 9.8 m/s2. If an object is moved to a location where g = 0, its mass:

The force with which the Earth attracts an object is called:

Two stars of masses m and 2m at a distance d rotate about their common centre of mass in free space. Their period of revolution is: