Exercises For the exercises in this chaP'er (and subsequent chapters), use the more urate value of g = 9.8 rule2 for die acceleration due to act: 31;\"); horizontally directed force of 40 N is used to pull a box a disrance of 1.5 in across a tabletop. How much work is done by the 40-N force? 52 A woman does 210 l of work to move a table 1.4 to across ' ' that the woman the oor. What rs the magnitude of the force . applied to the table if this force is applied in the horizontal direction? 133. A force of 80 N used to push a chair across a room does 320 l of work How far does the chair move in this process? 12-14. .A rope applies a horizontal force of 180 N to pull a crate a distance of 2 or across the floor. A frictional force of 70 N opposes this motion. a. What is the work done by the force applied by the rope? b. What is the work done by the frictional force? c. Wltat is the total workdone on the crate? E5. A force of 130 N is .used to drag a crate 4 in across a floor. The force is directed at an angle upward from the crate, so that the vertical component of the force is 120 N and the horizontal component is 50 N, as shown in the diagram. at. What is the work done by the horizontal component of the force\"! b. What is the work done by the vertical component of the force? c. What is the total work done by the l30-N force? E5 Diagram E6. A net force of 60 N accelerates a 4-kg mass over a distance E7. E8. E9. of 15 in. a. What is the work done by this not force? b. What is the increase in kinetic energy of the mass? A 0.3-kg ball has a velocity of 20 mls. a. What is the kinetic energy of the ball? b. How much work would be required to stop the ball? A box with a mass of 7.0 kg is lifted (without acceleration) through a height of 1.5 m, in order to place it on the shelf of a closet a. What is the increase in potential energy of the box? b. How much work was required to lift the box to this position? A leaf spring in an off-road truck with a spring constant k of 87.6 kN/m (87,600 Nlm) is compressed a distance of 6.2 cm (0.062 tn) from iB-original, unstretched position. What is the increase in potential energy of the spring (in kl)? 1310. To stretch a spring a distance of 0.30 Ell. E12. E13. E14. E15. E16. . ' . m from the equilib- rium position, 180 J of work is done. a. What is the increase in potential energy of the spring? b. What is the value of the spring constant k of the Spring? A i-kg rock is going to be moved either vertically or horizontally. a. What is the increase in the potential energy of the rock when lifting it to a height of 1.3 m Witho'" acceleration? What is the increase in kinetic energy to accelerate the same rock horizontally from rest to a speltd 0f 6 this? . Which requires more work: lifting the rock [.8 m 01' 30' celerating it horizontally to a speed of 6 mls? At the low point in its swing, a pendulum bob with a mass of 0.15 kg has a velocity of 3 rnls. a. What is its kinetic energy at the low point? b. What is its kinetic energy at the high point? c. What is its potential energy at the high point (assuming the potential energy at the low point was zero)? d. Ignoring air resistance. how high will the bob swing above the low point before reversing direction? A 0.40~kg mass attached to a spring is pulled back horizon- tally across a table. so that the potential energy of the sys- tem is increased from zero to 150 J. Ignoring friction. what is the kinetic energy of the system after the mass is released and has moved to a point where the potential energy has decreased to 60 J? A sled and rider with a combined mass of 70 kg are at the top of a hill that rises 9 m above the level ground below. The sled is given a push. providing an initial kinetic energy at the lap of the hill of 1200 J. a. Choosing a reference level at the bottom of the hill, what is the potential energy of the sled and rider at the top of the hill? b. Aer the push. what is the total mechanical energy of the sled and rider at the top of the hill? c. If friction can be ignored. what will be the kinetic energy of the sled and rider at the bottom of the hill? A roller-coaster car has a potential energy of 400,000 1 (400 kl) and a kinetic energy of 130,000 I (130 1d) at: point A in its travel. At the low point of the ride, the po- tential energy is zero, and 60,000 J (60 kl) of work has been done against friction since it left point A. What is the kinetic energy of the roller coaster at this low point (in kl)? A roller-coaster car with a mass of 900 kg starts at rest from a point 22 m above the ground. At point B. it is 8 m above the ground. [Express your answers in kilojoules (kl).] a. What is the initial potential energy of the car? b. What is the potential energy at point B? c._ If the initial kinetic energy was zero and the work done against friction between the starting point and point B is 30.000 J {30 kl). what is the kinetic energy of the car at point B? E17. A 300-g mass lying on a frictionless table is attached to a E18. The time required for one complete cycle of a mass oscillat- horizontal spring with a spring constant of 500 N/m. The ing at the end of a spring is 0.40 s. What is the frequency of spring is stretched a distance of 46 cm (0.46 m). oscillation? a. What is the initial potential energy of the system? E19. The frequency of oscillation of a pendulum is 16 cycles/s. b. What is the kinetic energy of the system when the mass What is the period of oscillation? returns to the equilibrium position after being released