Home Chapter 14 Multiple Choice

Multiple Choice

This activity contains 15 questions.

A car having a mass of 2 Mg strikes a smooth, rigid sign post with an initial speed of 30 km/h. To stop the car, the front end horizontally deforms 0.2 m. If the car is free to roll during the collision, determine the average horizontal collision force causing the deformation.

 Favg = 4500 kN Favg = 9000 kN Favg = 347 kN Favg = 694 kN

A car is equipped with a bumper B designed to absorb collisions. The bumper is mounted to the car using pieces of flexible tubing T. Upon collision with a rigid barrier A, a constant horizontal force F is developed which causes a car deceleration of 3g = 29.43 m/s2 (the highest safe deceleration for a passenger without a seatbelt). If the car and passenger have a total mass of 1.5 Mg and the car is initially coasting with a speed of 1.5 m/s, compute the magnitude of F needed to stop the car and the deformation x of the bumper tubing.

 F = 44.1 kN, x = 38.2 mm F = 22.1 kN, x = 76.4 mm F = 22.1 kN, x = 38.2 mm F = 44.1 kN, x = 76.4 mm

A car, assumed to be rigid and having a mass of 800 kg, strikes a barrel-barrier installation without the driver applying the brakes. From experiments, the magnitude of the force of resistance Fr, created by deforming the barrels successively, is shown as a function of vehicle penetration. If the car strikes the barrier traveling at Vc = 70 km/h, determine approximately the distance s to which the car penetrates the barrier.

 s = 1.890 m s = 4.72 m s = 2.77 m s = 2.52 m

When at A the bicyclist has a speed of vA = ft/s. If he coasts without pedaling from the top of the hill at A to the shore of B and then leaps off the shore, determine his speed at B and the distance x where he strikes the water at C. The rider and his bicycle have a total weight of 150 lb. Neglect the size of the bicycle and wind resistance.

 vB = 35.0 ft/s, x = 41.2 ft vB = 35.0 ft/s, x = 36.1 ft vB = 40.1 ft/s, x = 46.5 ft vB = 40.1 ft/s, x = 52.0 ft

The coefficient of friction between the 2-lb block and the surface is = 0.2. The block is acted upon by a horizontal force of P. Determine the maximum deformation of the outer spring B at the instant the block comes to rest. Spring B has a stiffness of KB = 20 lb/ft and the "nested" spring C has a stiffness of kc = 40 lb/ft.

 xB = 1.154 ft xB = 0.790 ft xB = 0.923 ft xB = 1.137 ft

The "flying car" is a ride at an amusement park, which consists of a car having wheels that roll along a track mounted on a drum. Motion of the car is created by applying the car's brake, thereby gripping the car to the track and allowing it to move with a speed of vt = 3m/s. If the rider applies the brake when going from B to A and then releases it at the top of the drum, A, so that the car coasts freely down along the track to B ( = rad), determine the speed of the car at B and the normal reaction which the drum exerts on the car at B. The rider and car have a total mass of m = 250 kg and the center of mass of the car and rider moves along a circular path of radius r = 8 m.

 vB = 12.88 m/s, NB = 2.45 kN vB = 12.88 m/s, NB = 7.64 kN vB = 17.97 m/s, NB = 12.54 kN vB = 17.97 m/s, NB = 7.64 kN

A motor hoists a 50-kg crate at constant speed to a height of h = 6 m in 3 s. If the indicated power of the motor is 4 kw, determine the motor's efficiency.

 e = 0.025 (2.5%) e = 0.245 (24.5%) e = 0.736 (73.6%) e = 0.05 (5.0%)

A truck has a weight of 25,000 lb and an engine which transmits a power of 350hp. Assuming that the wheels do not slip on the ground, determine the angle of the largest incline the truck can climb at a constant speed of v = 50 ft/s.

 2 = 8.86E 2 = 24.3E 2 = 8.75E 2 = 26.8E

The elevator E and its freight have a total mass of 400 kg. Hoisting is provided by the motor M and the 60-kg block C. If the motor has an efficiency of e = 0.6, determine the power that must be supplied to the motor when the elevator is hoisted upward at a constant speed of vE = m/s.

 P = 22.2 kW P = 13.34 kW P = 26.2 kW P = 30.1 kW

An electric train car, having a mass of 25 Mg, travels up a 10° incline with a constant speed of 80 km/h. Determine the power required to overcome the force of gravity.

 P = 961 kW P = 346 kW P = 341 kW P = 946 kW

The block has a weight of 1.5 lb and slides along the smooth chute AB. It is released from rest at A, which has coordinates of A(5 ft, 0, 10 ft). Determine the speed at which it slides off at B, which has coordinates of B(0, 8 ft, 0).

 vB = 28.7 ft/s vB = 25.4 ft/s vB = 26.8 ft/s vB = 29.8 ft/s

The firing mechanism of a pinball machine consists of a plunger P having a mass of 0.25 kg and a spring of stiffness k = 300 N/m. When s = 0, the spring is compressed 50 mm. If the arm is pulled back such that s = 100 mm and released, determine the speed of the 0.3 kg pinball B just before the plunger strikes the stop, i.e., s = 0. Assume all sufaces of contact to be smooth. The ball moves in the horizontal plane. Note that the ball slides without rolling.

 v = 4.47 m/s v = 3.30 m/s v = 2.34 m/s v = 3.16 m/s

The book A having a weight of 1.5 lb slides on the smooth horizontal slot. If the block is drawn back so that s = 0. Each of the two springs has a stiffness of k = 150 lb/ft and an unstretched length of 0.5 ft.

 vA = 106.2 ft/s vA = 120.4 ft/s vA = 160.5 ft/s vA = 107.7 ft/s

The roller-coaster car has a speed of 15 ft/s when it is at the crest of a vertical parabolic track. Compute the velocity and the normal force it exerts on the track when it reaches point B. Neglect friction and the mass of the wheels. The total weight of the car and the passengers is 350 lb.

 vB = 114.5 ft/s, NB = 29.1 lb vB = 114.5 ft/s, NB = 284 lb vB = 114.5 ft/s, NB = 156.5 lb vB = 114.5 ft/s, NB = 440 lb

The car C and its contents have a weight of 600 lb, whereas block B has a weight of 200 lb. If the car is released from rest, determine its speed when it travels 30 ft down the 20° incline.

 vC = 3.55 ft/s vC = 3.94 ft/s vC = 17.68 ft/s vC = 15.94 ft/s