Problem Set (engineering mechanics)

Prob.1 The 3500-lb automobile is traveling down the 10degree inclined road at a speed of 20ft/s. If the driver wishes to stop the car, determine how far his tires skid on the road if he jams on the brakes causing his wheels to lock. The coefficient of kinetic friction between the wheels and the road is uA= 0.5.

Prob2. The bus B has a weight of 15,000 lb and is traveling to the right at 5ft/s. Meanwhile a 3,000 lb car A is traveling at 4ft/s to the left. If the vehicles crash head-on and become entagled, determine their common velocity just after the collision. Assume that the brakes are not applied during collision.

Prob3. 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=(3200tsquare)N, where t is in seconds. If the car has an initial velocity V1=2m/s when t=0, determine its velocity when t= 2s.

Prob4. A 2-lb pendulum bob is released at theta=0 degree with a velocity Vo. When it reaches the lower position theta=90 degrees, a 0.1 lb bullet strikes the bob from below with a velocity of 1600 ft/s and becomes embedded in the bob in 0.2 after the initial contact. Determine the minimum velocity Vo fo the bob so that when the impact occurs the cord OC does not become slack. Assume the bullet creates a constant force on the bob during the impact.

Prob5. The 150 lb fireman is holding a hise which has a nozzle diameter of 1 in.a and hose diameter of 2in. If the velocity of the water at discharge is 60ft/s, determine the resultant normal and frictional force acting on the amn's feet at the ground. Neglecy the weight of the hose and the water within it. Gamma weight = 62.4 lb/ft cube.

Prob6. A golf ball struck on earth rises to a maximum height of 20ft & hits the ground 250 yards away. How far will the same golf ball travel on the moon if the magnitude & the direction of its velocity are the same as they were on earth immediately after the ball was hit? Assume that the ball is hit and lands at the same elevation in both cases and that the effect of the atmosphere on earth is neglected so that the trajectory in both cases is a parabola. The acceleration of gravity on the moon is 0.165 times that on earth.

Prob7. A baseball player catching a ball can soften the impact by pulling his hand back. Assuming that a 5-oz ball reaches his gloce at 90mi/h and that the player pull his hand back during the impact at an average speed of 30ft/s, over a distance of 6 inches,, bringing the ball to a stop, determine the average impulsive force exerted on the player's hand.

Prob8. Just for fun, two 750-N engineering students A and B intend to jump off the bridge from rest using an elastic cord (bungee cord) having a stiffness k= 1300 N/m. They wish to just reach the surface of the river, when A, attached to the cord, lets go of B at the instant they touch the water. Determine the proper unstretched length of the cord to the stunt, and calculate the maximum acceleration of student A and the maximum height he reaches, comment on the feasibility of doing the stunt.

Prob9. The tenns ball is struck with a horizontal velocity Vo that strikes the ground at B, and bounces upward at angle=30 degrees. Det. the initial velocity Vo, the final velocity Vb, and the coefficient of restitution between the ball and the ground.