Light always moves at the same speed. true or false

False

Light can travel through various materials like air, glass, water, oil, diamond etc. The speed of light is greatest in air and reduces as the material is dense. The light travels slowest in diamond. So, light travels with different speeds in different materials. In one material it travels with same speed always. The speed changes after zone boundary of any material.

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s

the answer is a. hope this .