Question

5 , 6, 7 Question Please answer need urgent

Answer 1

4. bronze ( copper and tin)
brass. ( copper and zinc)

5. Given in the question :-
Planet mass is 8 times that earth
Planet radius is twice then the radius of earth.
Let mass of the Earth = M
Radius of the Earth = R

Now, we know that The equation to get escape velocity 

v = √(2 g r)

If the mass of planet is eight times then escape velocity = 2 √2 times. 

Escape velocity reduced to by 1/√2. If radius expands twice
Hence the net escape velocity will be increase.

2 √2 ×  (1/√2)= 2 times now.
Now it is clear that the escape velocity of that planet will be 2 times from the earth.

Escape velocity of the earth = 11.2 km/s
Escape velocity of that planet = 2 × 11.2 = 22.4 km/sec.

Hence the escape velocity of that planet will be 22.4 km/s

6. Ans is in pic

7. Yes , sometimes it is an desirable for example in cinema hall when sound is reflected it may disturb the audience. We see everything because of reflection (diffused reflection) like walls, houses, doors, chairs, tables, gold etc.