Answer:
61.22m
Explanation:
Maximum height in projectile is expressed as;
H = u²sin²θ/2g
u is the speed
g is the acceleration due to gravity
θ is the angle of projection
Substitute the given values into the formula;
H = u²sin²θ/2g
H = 40²sin²60/2g
H = 1600(0.8660)²/2(9.8)
H = 1600(0.8660)²/2(9.8)
H = 1,199.9/19.6
H = 61.22m
Hence the maximum height achieved by the ball is 61.22m
The density of the fluid is 776.3 
<u>Explanation:</u>
Buoyant force is the upward pushing force whenever an object is trying to get immersed in fluid. So this is the force given by the fluid on the object which is trying to get immersed. The buoyant force is found to be directly proportional to the product of density of the object, volume of the object. And here the acceleration due to gravity will be acting as proportionality constant.

As, buoyant force is given as 671 N and volume is 0.0882
and acceleration is known as 9.8 m/
. Then density is

Thus,

Density is 776.3 kg
.
-- The unit of frequency is "per second" (Hz), which is [reciprocal time].
-- The unit of period is "second", which is [time].
Do you see where this is going ?
'Frequency' and 'period' are reciprocals of each other.
For any wave ...
Period = (1) / (frequency) .
Frequency = (1) / (period) .