Answer:
Solution given:
No of waves[N] =20crests & 20 troughs
=20waves
Time[T]=4seconds
distance[d]=3cm=0.03m
Now
<u>Wave</u><u> </u><u>length</u><u>=</u>3cm=3 × 
<u>Frequency</u>=
=
=5Hertz
and
Wave speed:wave length×frequency=3 ×
×5=1.5 ×
.
Answer:
Option (D) is correct.
Explanation:
The balloon lands horizontally at a distance of 420 m from a point where it as released.
Velocity of air balloon along +X axis =10 m/s
velocity of ball=4 m/s along + X axis
the velocity of balloon gets added to the velocity of ball. So the resultant velocity of the balloon=10+4 = 14 m/s
time taken= 30 s
The distance traveled is given by d= v t
d= 14 (30)
d= 420 m
Thus the balloon lands horizontally at a distance of 420 m from a point where it as released.
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The time taken by the ballast bag to reach the ground is 2.18 s
The ballast bag at rest with respect to the balloon has the upward velocity (u) of 4.6 m/s , which is the velocity of the balloon. When it is dropped from the balloon, its motion is similar to an object thrown upwards with an initial velocity <em>u </em>and it falls under the acceleration due to gravity<em> g.</em>
Taking the upward direction as positive and the downward direction as negative, the following equation of motion may be used.

The bag makes a net displacement <em>s</em> of 13.4 m downwards, hence

Its initial velocity is

The acceleration due to gravity acts downwards and hence it is negative.

Use the values in the equation of motion and write an equation for t.

Solving the equation for t and taking only the positive value for t,
t=2.18 s