Q: A 30.0 kg hammer, moving with speed 20.0m/s, strikes a steel spike 2.30 cm in diameter. The hammer rebounds with speed 10.0 m/s after 0.110s. What is the average stress in the spike during the impact?
(a) 1.97 × 107 N/m²
(b) 3.2 ×107 N/m²
(c) 4.6 × 107 N/m²
(d) 8.2 ×107 N/m²
Force = Change in momentum per sec.
Change in momentum = 2 m u (since hammer rebounds with same speed)
Q: Two rods of different materials having coefficient of thermal expansion α1, α2 and Young’s moduli Y1, Y2 respectively are fixed between two rigid massive walls. The rods are heated such that they undergo the same increase in temperature. There is no bending of the rods. If α1 : α2 = 2 : 3, the thermal stresses developed in the two rods are equal provided Y1 : Y2 is equal to:
Q: A wire of cross section A is stretched horizontally between two clamps located ‘2l’ m apart. A weight W kg is suspended from the mid-point of the wire. If the mid-point sags vertically through a distance x << l the strain produced is
Q: One end of a long metallic wire of length L, area of cross-section A and Young’s modulus Y is tied to the ceiling. The other end is tied to a massless spring of force constant K. A mass m hangs freely from the free end of the spring. It is slightly pulled down and released. Its time period is given by