Block A in the figure below has mass 0.700kg , and block B has mass 2.90kg . The
ID: 1373380 • Letter: B
Question
Block A in the figure below has mass 0.700kg , and block B has mass 2.90kg . The blocks are forced together, compressing a spring S between them; then the system is released from rest on a level, frictionless surface. The spring, which has negligible mass, is not fastened to either block and drops to the surface after it has expanded. Block B acquires a speed of 1.15m/s
What is the final speed of block A?
How much potential energy was stored in the compressed spring?
Please explain
Block A in the figure below has mass 0.700kg , and block B has mass 2.90kg . The blocks are forced together, compressing a spring S between them; then the system is released from rest on a level, frictionless surface. The spring, which has negligible mass, is not fastened to either block and drops to the surface after it has expanded. Block B acquires a speed of 1.15m/s What is the final speed of block A? How much potential energy was stored in the compressed spring? Please explainExplanation / Answer
a)
Initial vleocity of both blocks is zero.
From the law of conservation of momentum
0 = m1v1 + m2v2
So the velocity of block A is
v1 = - (m2v2)/m1
= - (2.90 kg)(-1.15 m/s)/(0.70 kg)
= 4.76 m/s
b)
From the law of conservation of energy , total energy of the system is conserved.
The potential energy stored in the spring = total kinetic energy of system
U = (1/2)m1v1^2 + (1/2)m1v2^2
= (1/2)(0.70 kg)(4.76 m/s)^2 + (1/2)(2.90 kg ) (1.15 m/s)^2
= 9.85 J