5. The 100-kg stone shown in Fig. a is originally at rest on the smooth horizontal surface. If a towing force of 200 N, acting at an angle of 45, is applied to the stone for 10 s, determine the final velocity and the normal force which the surface exerts on the stone during this time interval. 45 200 N (a) 6. If motor M exerts a force of F = (10t + 100) N on the cable, where t is in seconds, determine the velocity of the 25-kg crate when t = 4 s. The coefficients of static and kinetic friction between the crate and the plane are s = 0.3 and k = 0.25, respectively. The crate is initially at rest. M 7. The crate has a mass of 80 kg and is being towed by a chain which is always directed at 20 from the horizontal as shown. Determine the crate's acceleration in t = 2 s if the coefficient of static friction is s = 0.4, the coefficient of kinetic friction is k = 0.3, and the towing force is P = (90t) N, where t is in seconds.