A horizontal block-spring system with the block on a frictionless surface has to
ID: 1446097 • Letter: A
Question
A horizontal block-spring system with the block on a frictionless surface has total mechanical energy E = 55.0 J and a maximum displacement from equilibrium of 0.268 m. (a) What is the spring constant? N/m (b) What is the kinetic energy of the system at the equilibrium point? J (c) If the maximum speed of the block is 3.45 m/s, what is its mass? kg (d) What is the speed of the block when its displacement is 0.160 m? m/s (e) Find the kinetic energy of the block at x = 0.160 m. J (f) Find the potential energy stored in the spring when x = 0.160 m. J (g) Suppose the same system is released from rest at x = 0.268 m on a rough surface so that it loses 15.9 J by the time it reaches its first turning point (after passing equilibrium at x = 0). What is its position at that instant? m
Explanation / Answer
part a )
E = 55 J
A = 0.268 m
E = 1/2*kA^2
k = 1531.52 N/m
part b )
At equilibrium, point kinetic energy = total mechanical energy = 55J
part c )
E = 1/2m*vmax^2
m = 2E/vmax^2
m = 9.24 kg
part d )
E = 1/2kx^2 + 1/2mv^2
now displacement = 0.160 m
55 = 19.6J + 1/2*9.24*v^2
v = 2.768 m/s
part e )
KE = 1/2*mv^2
v = 2.768
KE = 35.4 J
part f )
total energy = KE + PE
55 = 35.4 + PE
PE = 19.6 J
part g )
PE initially = 1/2*kx^2 = 55J
PE2 + KE2 = PE1 + KE1 - 15.9
KE1 = 0
KE2 = 0
PE2 = 39.1 J
1/2*kx^2 = 39.1
x = 0.226 m
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