H.W.#4 from Serway Textbook Ch.7,8,9 Due Feb17,08

Ch.7

12. The force acting on a particle is Fx = (8x – 16) N, where x is in meters.

(a) Make a plot of this force versus x from x = 0 to x = 3.00 m. (b) From your graph, find the net work done by this force on the particle as it moves from

x = 0 to x = 3.00 m.

13. A particle is subject to a force Fx that varies with position as in Figure P7.13. Find the work done by the force on the particle as it moves

(a) from x = 0 to x = 5.00 m, (b) from x = 5.00 m to x = 10.0 m, and

(c) from x = 10.0 m to x = 15.0 m. (d) What is the total work done by the force over the distance x = 0 to x = 15.0 m?

15. When a 4.00-kg object is hung vertically on a certain light spring that obeys Hooke's law, the spring stretches 2.50 cm. If the 4.00-kg object is removed, (a) how far will the spring stretch if a 1.50-kg block is hung on it, and (b) how much work must an external agent do to stretch the same spring 4.00 cm from its unstretched position?

24. A 0.600-kg particle has a speed of 2.00 m/s at point A and kinetic energy of 7.50 J at point B. What is (a) its kinetic energy at A? (b) its speed at B? (c) the total work done on the particle as it moves from A to B?

26. A 3.00-kg object has a velocity . (a) What is its kinetic energy at this time? (b) Find the total work done on the object if its velocity changes to . (Note:From the definition of the dot product, v2 = v·v.)

Ch 8

10.An object of mass m starts from rest and slides a distance d down a frictionless incline of angle . While sliding, it contacts an unstressed spring of negligible mass as shown in Figure P8.10. The object slides an additional distance x as it is brought momentarily to rest by compression of the spring (of force constant k). Find the initial separation d between object and spring.

Figure P8.10

11.A block of mass 0.250 kg is placed on top of a light vertical spring of force constant 5 000 N/m and pushed downward, so that the spring is compressed by 0.100 m. After the block is released from rest it travels upward and then leaves the spring. To what maximum height above the point of release does it rise?

34.A 15.0-kg block is dragged over a rough, horizontal surface by a 70.0-N force acting at 20.0° above the horizontal. The block is displaced 5.00 m, and the coefficient of kinetic friction is 0.300. Find the work done on the block by (a) the 70-N force, (b) the normal force, and (c) the gravitational force. (d) What is the increase in internal energy of the block-surface system due to friction? (e) Find the total change in the block’s kinetic energy.

From Holliday Textbook

(Ch.8) 11E. Figure 8.25 show an 8 kg stone resting on a spring. The spring is compressed 10 cm by the stone. (a) What is the spring constant? (b) The stone is pushed down an additional 30 cm and released. What is the potential energy of the compressed spring just before thatrelease.

(c) How high above the release position will the stone rise?

Ch.9

Problem 10-6 A ballistic pendulum is a device that was used to measure the speeds of bullets before electronic timing devices were developed. The device consists of a large block of wood of mass M=5.4 kg, hanging from two long cords. A bullet of mass m=9.5 g is fired into the block, coming quickly to rest. The block+bullet then swing upward, their center of mass rising a vertical distance h = 6.3 cm before the pendulum comes momentarily to rest at the end of its arc.

(a)What was the speed v of the bullet just prior to the collision?

(b)What is the initial kinetic energy of the bullet? How much of this energy remains as mechanical energy of the swinging pendulum?

From Serway Textbook

Example: A 1500 kg car traveling east with a speed of 25 m/s collides at an intersection with a 2500 kg van traveling north at a speed of 20 m/s.

Find the direction and magnitude of the velocity of these vehicles after the

collision, assuming that the vehicles undergo a perfectly inelastic collision.