21.A ball of mass M is thrown vertically upwards. Another ball of mass 2M is thrown at an angle ? to vertical. Both of them stay in air for the same period of time, the heights attained by the two are in the ratio:

22.If retardation produced by air resistance to the projectile is one-tenth of acceleration due to gravity, the time to return from the maximum height:

23.When the range of a projectile on an inclined plane is maximum then:

24.In the case of an oblique projectile, the velocity is perpendicular to acceleration

25.The range of projectile projected at an angle 15 degree is 10v3 m. If it is fired with the same speed at angle of 30 degree, its range will be: