A block of wood has a height of 10 m, a length of 2 m, and a width of 2 m. What is the volume of the block of wood?
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Answer:
x =
Explanation:
Let's start the exercise with the definition of a system formed by the projectile and the block, in this case the forces during the collision are internal and the moment is conserved,
initial instant. Just before the crash
p₀ = m v + 4m 0
final instant. Right after the crash, before the block began to move
= (m + 4m) v_{f}
how the moment is preserved
p₀ = p_{f}
m v = 5m v_{f}
v_{f} = v/5
knowing the speed of the system (projectile + block) we can use the relationship between work and energy
W = ΔK
starting point. Just when the projectile + block system starts to move
Em₀ = K = ½ m v_{f}²
final point. When the system is stopped
Em_{f} = 0
The work of the friction force is
W = - fr x
the negative sign is because the friction force opposes the motion, let's use Newton's second law to find the friction force
Y Axis
N- W = 0
N = W = mg
The expression for the friction force is
fr = μ N
substituting
fr = μ mg
W = - μ mg x
using the energy duty ratio
- μ mg x = 0 - ½ m
x =
we substitute speed
x =