CHAPTER I.MECHANroS
3f
Prove that after the spring is fully expanded and its action ceases the carts will move along horizontal rails in -such a way that their centre of mass (centre of gravity) remains at rest. Disregard friction. 9.1. A grenade flying in a horizontal direction with a velocity Vo = 10 mls bursts into two fragments weighing Pi = 1 kgf and P 2 = 1.5 .kgf. After the burst the velocity of the larger fragment remains horizontal and increases to V2 = 25 m/s. .
Fig. 28
Find the speed and direction of the smaller fragment. 92. The world's first reactive projectile invented by the Russian general A. D. Zasyadko (1779-1838) weighed about 2 kgf (without the propellant charge). The explosion of the propellant charge ejected 200 g of powder gases from the projectile at a velocity u = 600 m/s. At what distance from the point of projection will such a body fall, if it is launched at an angle a, = 45° to the horizontal? Disregard the air resistance.
Fig 29.
L
93. A cart filled with sand rolls at a speed V2 = 1 m/s along a horizontal path without friction (Fig. 29). A ball of mass m = 2 kg is thrown with a horizontal velocity Vi = 7 m/s towards the cart. The ball meets the cart and gets stuck in the sand. In what direction and with what velocity u will the cart move after the ball strikes it? The mass of the cart is M = = 10 kg. 94. Assume that the jet engine of a rocket ejects the