Determine the springs needed to absorb the energy:
A vehicle weighing 28 kN and running at 2.5 m/sec is to be brought to rest by a buffer springs. Determine the number of springs needed to absorb the kinetic energy if n = 20
Compression of each spring = 200 mm
Diameter of wire = 30 mm
Radius of coil = 100 mm
G = 80 GPa
Solution
KE = 1 mV^{ 2} = 1 (28 × 10^{3} /9.81) × 2.5^{2 } = 8919.5 N-m
Δ= 64 W R^{3} n / Gd ^{4}
⇒ 200 =64 × W × 100^{3 }× 20 / (80 × 10^{3} ) × (30)^{4}
∴ W = 10125 N
For one spring, U = 1 W Δ = 1 × 10125 × (200/1000) = 1012.5 N-m
∴ Numbers of springs, N = KE /U= 8919.5 /1012.5= 8.8 ; 9.0