Chapter 15, Problem 15P

The conveyor belt delivers each 12-kg crate to the ramp at A such that the crate’s speed is vA = 2.5 m>s,directed down along the ramp. If the coefficient of kinetic friction between each crate and the ramp is mk = 0.3,determine the smallest incline u of the ramp so that the crates will slide off and fall into the cart

The 56.28 kg crate is hoisted up the 0 = 27° incline by the pulley system and motor M. If the crate starts from rest and, by constant acceleration, attains a speed of 8.17 m/s after traveling 7.84 m along the plane, determine the supplied power to the motor if the crate has moved 8 m and the coefficient of kinetic friction between the plane and the crate is Hk = 0.3. Neglect friction along the plane. The motor has an efficiency of 0.691. M

The 300-kg bar B, originally at rest, is being towed over a series of small rollers. Determine the force in the cable when t = 5s, if the motor M is drawing in the cable for a short time at a rate of v = (0.47²) m/s, where t is in seconds (0 <= t<= 6 s). How far does the bar move in 5s? Neglect the mass of the cable, pulley, and the rollers. M B

1. The 400-kg mine car is hoisted up the incline using the cable and motor M. For a short time, the force in the cable is F = (3200f²) N, where t is in seconds. If the car has an initial velocity v₁ = 2 m/s at s = 0 and t=0, determine the distance it moves up the plane when t = 2 s. 17 15 v₁ = 2 m/s

The 50-lb crate is subjected to the force F = 40 lb. The coefficient of kinetic friction between the crate and the ground is µk = 0.2. If the crate is initially moving to the right with a velocity of 3 ft/s, determine A) The speed of the block when t = 8 s. B) The power developed by force F at t = 8 s.

At the instant shown the 2.3 kg collar is moving to the left on the horizontal shaft with a speed of 5.7 m/s that is increasing at a rate of 4.3 m/s/s in spite of the 11 N friction force between the collar and shaft. Determine the force of the spring in N. Assume s = 4.0 m, h = 2.2.  Express the result in N.

The rod of the fixed hydraulic cylinder is moving to the left with a speed of 94 mm/s and this speed is momentarily increasing at a rate of 440 mm/s each second at the instant when SA = 355 mm. Determine the tension in the cord at that instant. The mass of slider Bis 0.77 kg, the length of the cord is 950 mm, and the effects of the radius and friction of the small pulley at A are negligible. Find results for cases (a) negligible friction at slider B and (b) p = 0.42 at slider B. The action is in a vertical plane. 220 mm Answers: 0.77 kg B (a) Negligible friction: T= i (b) Uk=0.42: T= i N N

2. Crates A and B weigh 100 lb and 50 lb, respectively. If they start from rest, determine their speed when t = 5 s. Also, find the force exerted by crate A on crate B during the motion. The coefficient of kinetic friction between the crates and the ground is = 0.25. A P = 50 lb B

3. The 60-lb boy swings down as shown in Fig. below. If he starts from rest when 0 = 0°, determine the rate of change in his speed and the tension on each of the two cords of the swing when 0 = 60°. Neglect his size and the mass of seat and cords for the calculation. His speed is actually the speed of boy's center of mass G.