Speed = Distance/ Time
Speed = 400 / 4
Speed = 100 km/hr.
100 km per hour.
The wavelength was doubled, and its energy will be increased by 4 times.
looking at the formula
energy 
also, 
hence it is clear from above that energy is directly proportional to the square of the wavelength.
hence, The wavelength was doubled, and its energy will be increased by 4 times.
<h3>
What is Wavelength?</h3>
- The distance over which a periodic wave's shape repeats is known as the wavelength in physics.
- It is a property of both traveling waves and standing waves as well as other spatial wave patterns. It is the distance between two successive corresponding locations of the same phase on the wave, such as two nearby crests, troughs, or zero crossings.
- The spatial frequency is the reciprocal of the wavelength. The Greek letter lambda is frequently used to represent wavelength.
- The term wavelength is occasionally used to describe modulated waves, their sinusoidal envelopes, or waves created by the interference of several sinusoids.
To learn more about wavelength with the given link
brainly.com/question/13533093
#SPJ4
Answer:
Acceleration of that planet is 30
.
Given:
initial speed of hammer = 0 
time = 1 s
distance = 15 m
To find:
Acceleration due to gravity = ?
Formula used:
Distance covered by hammer is given by,
s = ut + 
s = distance
u = initial speed of hammer
t = time taken by hammer to reach ground
a = acceleration
Solution:
Distance covered by hammer is given by,
s = ut + 
s = distance
u = initial speed of hammer
t = time taken by hammer to reach ground
a = acceleration
u = 0
t = 1 s
s = 15 m
a = g
Thus substituting these value in above equation.
15 = 0 + 
g = 15 × 2
g = 30 
Thus, acceleration of that planet is 30
.