Raindrops fall to the ground with a uniform, constant velocity. This constant velocity is achieved when the gravitational pull is perfectly balanced by: MCQ with Answer and Explanation

Explanation:
g = GM/R², where M is mass of Earth, R radius, G universal constant. It does not depend on mass of falling object (Galileo's experiment). Earth's rotation causes slight variation but surface g is primarily determined by M and R. So mass of Earth is factor.

Explanation:
At maximum height, vertical velocity becomes zero momentarily. However, acceleration due to gravity (g) acts downward throughout the motion, including at the peak. Thus acceleration is g ≈ 9.8 m/s² downward, not zero. Memory tip: 'Peak of projectile: v=0, a=g downward'. This conceptual question tests understanding of motion under gravity, frequently appearing in competitive exams. Always distinguish velocity (which changes) from acceleration (constant in free fall near Earth). Misconception that acceleration is zero at peak is a common trap.

Explanation:
When light travels from an optically denser medium to a rarer medium, it bends away from the normal. As the angle of incidence increases, the angle of refraction also increases. The specific angle of incidence for which the refracted ray grazes the surface (meaning the angle of refraction is exactly 90 degrees) is defined as the critical angle.