Answer: More friction
Explanation: The wood would probably splinter, causing even more friction, while the metal would probably smooth the wood out.
Gravitational acceleration, g = GM/r^2. Additionally, for a satellite in a circular orbit, g = v^2/r
Where, G = Gravitational constant, M = Mass of earth, r = distance from the center of the earth to the satellite, v = linear speed of the satellite.
Equating the two expressions;
v^2/r = GM/r^2
v = Sqrt (GM/r);
But GM = Constant = 398600.5 km^3/sec^2
r = Altitude+Radius of the earth = 159+6371 = 6530 km
Substituting;
v = Sqrt (398600.5/6530) = 7.81 km/sec = 781 m/s
Answer:
F = 4000 N
Explanation:
given,
mass of rocket (M)= 5000 Kg
10 Kg gas burns at speed (m)= 4000 m/s
time = 10 s
average force = ?
at the end the rocket is at rest
by conservation of momentum
M v + m v' = 0
5000 x v - 10 x 4000 = 0
5000 v = 40000
v = 8 m/s
speed of rocket = 8 m/s
now,
we know
change in momentum = F x Δ t


F = 4000 N
Hence, the average force applied to the rocket is equal to F = 4000 N
To solve this problem we will apply the concept related to destructive interference (from the principle of superposition). This concept is understood as a superposition of two or more waves of identical or similar frequency that, when interfering, create a new wave pattern of less intensity (amplitude) at a point called a node. Mathematically it can be described as

Where,
d = Path difference
= wavelength
n = Any integer which represent the number of repetition of the spectrum
In this question the distance between the two source will be minimum for the case of minimum path difference, then n= 1



Therefore the minimum distance that should you separate two sources emitting the same waves is 2.5mm