Question

Dynamics

The UHart downhill racer team is testing a new design. There are 4 wheels each with a diameter of 0.4 m and a mass of 2.0kg. The rest of the cart has a mass of 20 kg. A spring-loaded brake applies a constant force of 50 N on the two rear wheels.The coefficient of friction between a brake pad and a wheel is0.7. The cart is traveling down a slope of 0 = 10° at 13.5km/hr when the brake is applied. Determine how far the racer will travel down the slope until it stops. Model the wheels as uniform thin discs.

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### Question 45555

Dynamics

*15-40. The boy jumps off the flat car at A with a velocity of v = 4 ft/s relative to the car as shown. If he lands on the second flat car B, determine the final speed of both cars after the motion. Each car has a weight of 80 lb. The boy's weight is 60 lb. Both cars are originally at rest. Neglect the mass of the car's wheels

### Question 45554

Dynamics

15-57. The 10-kg block is held at rest on the smooth inclined plane by the stop block at A. If the 10-g bullet is traveling at 300 m/s when it becomes embedded in the10-kg block, determine the distance the block will slide up along the plane before momentarily stopping.

### Question 45553

Dynamics

15-54. Solve Prob. 15-53 if the coefficient of kinetic friction between A and B is H = 0.3. Neglect friction between block B and the horizontal plane

### Question 45552

Dynamics

15-15. The motor, M, pulls on the cable with a force F=(10f + 300) N, where r is in seconds. If the 100 kg crate's originally at rest at t=0, determine its speed when t=4 s Neglect the mass of the cable and pulleys. Hint: First find the time needed to begin lifting the crate.

### Question 45551

Dynamics

15-22. The thrust on the 4-Mg rocket sled is shown in the graph. Determine the sleds maximum velocity and the distance the sled travels when t 35 s. Neglect friction.

### Question 45550

Dynamics

15-10. The 50-kg crate is pulled by the constant force P. Ifthe crate starts from rest and achieves a speed of 10 m/s in5 s, determine the magnitude of P. The coefficient of kinetic friction between the crate and the ground is Hi =0.2.

### Question 45549

Dynamics

*15-8. The automobile has a weight of 2700 lb and is-traveling forward at 4 ft/s when it crashes into the wall. Ifthe impact occurs in 0.06 s, determine the average impulsive force acting on the car. Assume the brakes are not applied. If the coefficient of kinetic friction between the wheels and the pavement is H = 0.3, calculate the impulsive force on the wall if the brakes were applied during the crash.The brakes are applied to all four wheels so that all the wheels slip.

### Question 45467

Dynamics

As a part of a robotics competition, a robotic arm with a rigid open hand at C is to be designed so that the hand catches an egg without breaking it. The egg is released from rest at t = 0 from point A. The arm, initially at rest in the position shown, starts moving when the egg is released. The hand must catch the egg without any impact with the egg. This can be done by specifying that the hand and the egg must be at the same position at the same time with identical velocities. A student proposes to do this using a constant value of 0 for which (after a fair bit of work) it is found that the arm catches the egg at /= 0.4391 s forÖ = -13.27 rad/s2. Using these values of t and Ö, determine the acceleration of both the hand and the egg at the time of catch.Then, explain whether or not using a constant value of 0, as has been proposed, is an acceptable strategy.

### Question 45466

Dynamics

A crate A is being pulled up an inclined ramp by a winch retracting the cord at a constant rate vo = 2 ft/s. Letting h =1.5 ft,determine the speed of the crate when d = 4 ft.

### Question 45463

Dynamics

At the instant shown, VB = 5 î m/s. If theta = 25°, determine the speed of A relative to B in order for A to travel only in the vertical direction while sliding over B.