Answer:
(A) The speed just as it left the ground is 30.25 m/s
(B) The maximum height of the rock is 46.69 m
Explanation:
Given;
weight of rock, w = mg = 20 N
speed of the rock at 14.8 m, u = 25 m/s
(a) Apply work energy theorem to find its speed just as it left the ground
work = Δ kinetic energy
F x d = ¹/₂mv² - ¹/₂mu²
mg x d = ¹/₂m(v² - u²)
g x d = ¹/₂(v² - u²)
gd = ¹/₂(v² - u²)
2gd = v² - u²
v² = 2gd + u²
v² = 2(9.8)(14.8) + (25)²
v² = 915.05
v = √915.05
v = 30.25 m/s
B) Use the work-energy theorem to find its maximum height
the initial velocity of the rock = 30.25 m/s
at maximum height, the final velocity = 0
- mg x H = ¹/₂mv² - ¹/₂mu²
- mg x H = ¹/₂m(0) - ¹/₂mu²
- mg x H = - ¹/₂mu²
2g x H = u²
H = u² / 2g
H = (30.25)² / 2(9.8)
H = 46.69 m
Answer: 3.41 s
Explanation:
Assuming the question is to find the time
the ball is in air, we can use the following equation:

Where:
is the final height of the ball
is the initial height of the ball
is the initial velocity of the ball
is the time the ball is in air
is the acceleration due to gravity

Then:


Multiplying both sides of the equation by -1 and rearranging:

At this point we have a quadratic equation of the form
, which can be solved with the following formula:
Where:
Substituting the known values:
Solving the equation and choosing the positive result we have:
This is the time the ball is in air
I think the answer A since temperature is the average kinetic energy of the molecules, so increasing temperature must increase kinetic energy
Mass of the bird(m) = 150 g = 0.15 kg
Speed (v) = 10 m/s
Kinetic Energy =
= 7.5 J
Altitude (h) = 15 m
Gravitational Potential Energy = (0.15)(9.81)(15) = 22.0725 J
Mechanical Energy = Kinetic Energy + Potential Energy = 7.5 + 22.0725
= 29.5725 J
Answer:

Explanation:
Speed of light is the product of its wavelength and frequency, expressed as
S=fw
Where s represent speed, f is frequency while w is wavelength
Making f the subject of the formula then
f=s/w
Substituting 2.99x10^8 m/s for s and 3.012x10^-12 m for w then

Therefore, the frequency equals to 