Complete question:
a 2.0 kg block slides on the horizontal, frictionless surface until it counters a spring with force constant of 955 N/m. The block comes to rest after compressing the spring a distance of 4.6 cm. Find the initial speed (in m/s) of the block.
Answer:
The initial speed of the block is 1.422 m/s
Explanation:
Given;
mass of the block, m = 2.0 kg
force constant of the spring, K = 955 N/m
compression of the spring, x = 4.6 cm = 0.046 m
Apply Hook's law to determine applied force on the spring;
F = Kx
F = (955 N/m)(0.046 m)
F = 43.93 N
Apply Newton's 2nd law to determine the magnitude of deceleration of the block when it encounters the spring;
F = ma
a = F / m
a = 43.93 / 2
a = 21.965 m/s²
Apply kinematic equation to determine the initial speed of the block;
v² = u² + 2ax
where;
v is the final speed of the block = 0
u is the initial speed of the block
x is the distance traveled by the block = compression of the spring
a is the block deceleration = -21.965 m/s²
0 = u² + 2(-21.965 )(0.046)
0 = u² - 2.021
u² = 2.021
u = √2.021
u = 1.422 m/s
Therefore, the initial speed of the block is 1.422 m/s
. Using Hook's law,
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