6. What net external force is required to give a 25 kg suitcase an acceleration of 2.2 m/s2 to the right? Draw a free-body diagram of the suitcase.

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1 HONORS PHYSICS PROBLEM SET NEWTON S LAWS & FORCES ONE DIMENSIONAL FORCES 1. The net external force on the propeller of a 0.75 kg model airplane is 17 N forward. What is the acceleration of the airplane? 2. The net external force on a golf cart is 390 N north. If the cart has a total mass of 270 kg, what are the magnitude and direction of its acceleration? 3. A car has a mass of 1.50 x 103 kg. What force is required to accelerate the car at 4.5 m/s 2 to the east? 4. A 2.0 kg mass starts from rest at the top of an inclined plane 85 cm long and slides down to the bottom in 0.50 s. What net external force acts on the mass along the incline? 5. A ball pushed with a force of 13.5 N accelerates at 6.5 m/s 2 to the right. What is the mass of the ball? 6. What net external force is required to give a 25 kg suitcase an acceleration of 2.2 m/s2 to the right? Draw a free-body diagram of the suitcase. 7. What acceleration will you give to a 24.3 kg box if you push it with a force of 85.5 N? 8. An 1850 kg car is moving to the right at a constant velocity of 1.44 m/s. a. What is the net force on the car? b. What would be the net force on the car if it were moving to the left? 9. A freight train has a mass of 1.5 x 10 7 kg. If the locomotive can exert a constant pull of 7.5 x 10 5 N, how long would it take to increase the speed of the train from rest to 85 km/h? 10. A loaf of bread weighs 5.30 N on Earth. a. What should it weigh, in newtons, on the moon, where the acceleration due to gravity is one-sixth that on Earth? b. What should it weigh on Jupiter, where g is 2.64 times Earth's gravity? 11. A 2.26 kg book is dropped from a height of 1.5 m. a. What is its acceleration? b. What is its weight in newtons? 12. A 3.46 kg briefcase is sitting at rest on a level floor. a. What is its acceleration? b. What is its weight in newtons? 13. What net external force is required to give a 25 kg suitcase an acceleration of 2.2 m/s 2 to the right? Draw a free-body diagram of the suitcase. 14. An 1850 kg car is moving to the right at a constant velocity of 1.44 m/s. a. What is the net force on the car? b. What would be the net force on the car if it were moving to the left? 15. A freight train has a mass of 1.5 x 10 7 kg. If the locomotive can exert a constant pull of 7.5 x 10 5 N, how long would it take to increase the speed of the train from rest to 85 km/h? (470 s) 16. A 5.0 kg bucket of water is raised from a well by a rope. If the upward acceleration of the bucket is 3.0 m/s 2, find the force exerted by the rope on the bucket of water.

2 17. A boat moves through the water with two forces acting on it. One is a 2.10 x 10 3 N forward push by the motor, and the other is a 1.80 x 10 3 N resistive force due to the water. a. What is the acceleration of the 1200 kg boat? (0.25 m/s 2 ) b. If it starts from rest, how far will it move in 12.0 s? (18 m) c. What will its velocity be at the end of this time interval? (3.0 m/s) 18. A 2.0 kg mass starts from rest and slides down an inclined plane 8.0 x 10 1 m long in 0.50 s. What net force is acting on the mass along the incline? (13 N down incline) 19. A shopper in a supermarket pushes a loaded 32 kg cart with a horizontal force of 12 N. a. How far will the cart move in 3.5 s, starting from rest? (Disregard friction.) b. How far will the cart move in 3.5 s if the shopper places an 85 N child in the cart before pushing? 20. A 75 kg person escapes from a burning building by jumping from a window 25 m above a catching net. Assuming that air resistance exerts a 95 N force on the person during the fall, determine the person's velocity just before hitting the net. 21. The parachute on a race car that weighs 8820 N opens at the end of a quarter-mile run when the car is traveling 35 m/s. What total retarding force must be supplied by the parachute to stop the car in a distance of 1100 m? (-500 N) 22. A 1250 kg car is pulling a 325 kg trailer. Together, the car and trailer have an acceleration of 2.15 m/s 2 directly forward. a. Determine the net force on the car. (2690 N) b. Determine the net force on the trailer. (699 N) TWO DIMENSIONAL FORCES 23. A man is pulling on his dog with a force of 70.0 N directed at an angle of to the horizontal. a. Find the x component of this force. b. Find the y component of this force. 24. The man pulls with a force of 25.0 N at an angle of 18.0 to the horizontal. a. Find the x component of this force. b. Find the y component of this force. 25. A crate is pulled to the right with a force of 85 N, to the left with a force of 115 N, upward with a force of 565 N, and downward with a force of 236 N. a. Find the net external force in the x direction. b. Find the net external force in the y direction. c. Find the magnitude and direction of the net external force on the crate. 26. Draw a free-body diagram representing each of the following objects: a. a ball in free fall in the presence of air resistance b. a helicopter lifting off a landing pad c. an athlete running along a horizontal track 27. Draw a force diagram for each of the following situations: a. A chair is pushed forward with a force of 185 N, the force of Earth on the chair is 155 N downward, and the floor exerts a force of 155 N upward on the chair. Draw a free-body diagram of the chair. b. The force of Earth on a cake on a plate is 8.9 N downward, the plate exerts a force of 11.0 N upward on the cake, and a knife exerts a downward force of 2.1 N on the cake. Draw a free-body diagram of the cake.

3 28. Four forces act on a hot-air balloon, shown from the side in Figure Find the magnitude and direction of the resultant force on the balloon. ( º) 29. Two lifeguards pull on ropes attached to a raft. If they pull in the same direction, the raft experiences a net external force of 334 N to the right. If they pull in opposite directions, the raft experiences a net external force of 105 N to the left. a. Draw a free-body diagram representing the raft for each situation. b. Find the force exerted by each lifeguard on the raft. (Disregard any other forces acting on the raft.) 30. A dog pulls on a pillow with a force of 5 N at an angle of 37 above the horizontal. Find the x and y components of this force. (4 N, 3 N) 31. A 3.00 kg ball is dropped from the roof of a building m high. While the ball is falling to Earth, a horizontal wind exerts a constant force of 12.0 N on it. a. How far from the building does the ball hit the ground? b. How long does it take to hit the ground? c. What is its speed when it hits the ground? 32. A block with a mass of 5.0 kg is held in equilibrium on an incline of angle 0 = 30.0 by the horizontal force, F, applied perpendicular to the incline. Find the magnitude of F. Find the normal force exerted by the incline on the block. (Disregard friction.) FRICTION AND NORMAL FORCE 33. A museum curator moves artifacts into place on many different display surfaces. Use the values in Table 4-2 to find Fs, max and F k for the following situations: a. moving a 145 kg aluminum sculpture across a horizontal steel platform (870 N, 670 N) b. pulling a 15 kg steel sword across a horizontal steel shield (110 N, 84 N) c. pushing a 227 kg wood bed on a wood floor d. sliding a 0.55 kg glass amulet on a glass display case (5 N, 2 N) 34. A 25 kg chair initially at rest on a horizontal floor requires a 365 N horizontal force to set it in motion. Once the chair is in motion, a 327 N horizontal force keeps it moving at a constant velocity. a. Find the coefficient of static friction between the chair and the floor. b. Find the coefficient of kinetic friction between the chair and the floor. 35. A box of books weighing 325 N moves with a constant velocity across the floor when it is pushed with a force of 425 N exerted downward at an angle of 35.2 below the horizontal. Find µ k between the box and the floor. (0.609)

4 36. A student moves a box of books down the hall by pulling on a rope attached to the box. The student pulls with a force of 185 N at an angle of 25 above the horizontal. The box has a mass of 35 kg, and μ k between box and floor is Find the acceleration of the box. (2.7 m/s 2 ) 37. The student in previous problem moves the box up a ramp inclined at 12 with the horizontal. If the box starts from rest at the bottom of the ramp and is pulled at an angle of 25 with respect to the incline and with the same 185 N force, what is the acceleration up the ramp? Assume that μ k = A 75 kg box slides down a 25 ramp with an acceleration of 3.6 m/s 2. a. Find μ k between the box and the ramp. b. What acceleration would a 175 kg box have on this ramp? 39. A 2.00 kg block is in equilibrium on an incline of angle θ = Find F of the incline on the block. 40. A 5.4 kg bag of groceries is in equilibrium on an incline of angle θ = 15. Find the normal force of the incline on the bag. 41. A box of books weighing 319 N is shoved across the floor by a force of 485 N exerted downward at an angle of 35 below the horizontal. a. If μ k between the box and the floor is 0.57, how long does it take to move the box 4.00 m, starting from rest? b. If μ k between the box and the floor is 0.75, how long does it take to move the box 4.00 m, starting from rest? 42. A 95 kg clock initially at rest on a horizontal floor requires a 650 N horizontal force to set it in motion. After the clock is in motion, a horizontal force of 560 N keeps it moving with a constant speed. Find,μ s and μ k between the clock and the floor. (0.70, 0.60) 43. A box slides down a 30.0 ramp with an acceleration of 1.20 m/s 2. Determine the coefficient of kinetic friction between the box and the ramp. (0.436) 44. A 40.0 kg wagon is towed up a hill inclined at 18.5 with respect to the horizontal. The tow rope is parallel to the incline and exerts a force of 140 N on the wagon. Assume that the wagon starts from rest at the bottom of the hill, and disregard friction. a. How fast is the wagon going after moving 30.0 m up the hill? b. How fast is the wagon going after moving 80.0 m up the hill? 45. A clerk moves a box of cans down an aisle by pulling on a rope attached to the box. The clerk pulls with a force of N at an angle of 25.0 with the horizontal. The box has a mass of 35.0 kg, and the coefficient of kinetic friction between box and floor is Find the acceleration of the box. 46. A car is traveling at 50.0 km/h on a flat highway. a. If the coefficient of friction between the road and the tires on a rainy day is 0.100, what is the minimum distance needed for the car to stop? b. What is the stopping distance when the surface is dry and the coefficient of friction is 0.600? 47. A 4.00 kg block is pushed along the ceiling with a constant applied force of 85.0 N that acts at an angle of 55.0 with the horizontal, as in Figure The block accelerates to the right at 6.00 m/s 2. Determine the coefficient of kinetic friction between the block and the ceiling. (0.816)

5 48. A 35 kg box rests on the back of a truck. The coefficient of static friction between the box and the truck bed is a. When the truck accelerates forward, what happens to the box? b. Find the maximum acceleration the truck can have before the box slides. 49. A girl coasts down a hill on a sled, reaching the bottom with a speed of 7.0 m/s. The coefficient of friction between the sled's runners and the snow is 0.050, and the girl and sled together weigh 645 N. How far does the sled travel on the surface before coming to rest? 50. A 3.00 kg block starts from rest at the top of a 30.0 incline and slides 2.00 m down the incline in 1.50s. a. Find the acceleration of the block. (1.78 m/s 2 ) b. Find the coefficient of kinetic friction between the block and the incline. (0.37) c. Find the frictional force acting on the block. (9.4 N) d. Find the speed of the block after it has slid a distance of 2.00 m. (2.67 m/s) 51. The coefficient of static friction between the 3.00 kg crate and the 35.0 incline is What is the minimum force, F, that must be applied to the crate perpendicular to the incline to prevent the crate from sliding down the incline? 52. A hockey puck is hit on a frozen lake and starts moving with a speed of 12.0 m/s. Exactly 5.00 s later, its speed is 6.00 m/s. a. What is its average acceleration? (-1.2 m/s 2 ) b. What is the average value of the coefficient of kinetic friction between puck and ice? (0.12)