Physics 1301 Problems Lecture 07 PDF

Problems Lecture 07 Work, Energy, and Energy Resources A 4.10 kg box of books is lifted vertically from rest a distance of 1.60 m with a constant, upward applied force of 52.7 N. (a) Find the work done by the applied force. (b) Find the work done by gravity. (c) Find the final speed of the box....

Problems Lecture 07 Work, Energy, and Energy Resources A 4.10 kg box of books is lifted vertically from rest a distance of 1.60 m with a constant, upward applied force of 52.7 N. (a) Find the work done by the applied force. (b) Find the work done by gravity. (c) Find the final speed of the box. Diane pulls a sled along a snowy path on level ground with her little brother Jasper riding on the sled. The total mass of Jasper and the sled is 26 kg. The cord’s tension is 41 N with a 20.0° angle with the ground, and the coefficient of friction on the sled is 𝜇𝑘 = 0.16. The sled moves moves 120 m along the path at a constant 3 km/h. (a) Find the work done by Diane. (b) Find the work done by the ground on the sled. (c) What is the total work done on the sled? A woman weighing 600 N steps on a bathroom scale that contains a stiff spring. In equilibrium, the spring is compressed 1.0 cm and the total under her weight. (a) Find the force constant of the spring. (b) Find the work done on the spring during the compression. In the bottom of the 9th inning, a player hits a 0.15 kg baseball over the outfield fence. The ball leaves the bat with a speed of 36 m/s, and a fan in the bleachers catches it 7.2 m above the point where it was hit. Assuming frictional forces can be ignored. (a) Find the kinetic energy of the ball just before it's caught. (b) Find the ball’s speed just before it's caught. A 350 kg roller coaster car starts from rest at point A and slides down a frictionless loop- the-loop. The car's wheels are designed to stay on the track. (a) How fast is this roller coaster car moving at point B. (b) How hard does it press against the track at point B? A 55-kg skateboarder enters a ramp moving horizontally with a speed of 6.5 m/s and leaves the ramp moving vertically with a speed of 4.1 m/s. (a) Find the height of the ramp, assuming no energy loss to frictional forces. (b) Find the maximum height the skateboarder reaches. A 1.70-kg block slides on a horizontal, frictionless surface until it encounters a spring with a force constant of 955 N/m. The block comes to rest after compressing the spring a distance of 4.60 cm. Find the initial speed of the block (Ignore air resistance and any energy lost when the block initially contacts the spring). Suppose the spring and block are oriented vertically. Initially, the spring is compressed 4.60 cm, and the block is at rest. When the block is released, it accelerates upward. (a) Find the speed of the block when the spring has returned to its equilibrium position. (b) Find the maximum height the block reaches from where it was released. A diver drops straight down from a platform 10 m above the water level of a swimming pool. As he enters the water, resistance slows him down until he stops 20 m below the water level. What is the work done by the water resistance on the diver? An 80.0-kg jogger starts from rest and runs uphill into a stiff breeze. At the top of the hill, the jogger has done the work Wnc1 = 18000 J, air resistance has done the work Wnc2 = −4420 J, and the jogger's final speed is 3.50 m/s. Find the height of the hill. A block of mass 𝑚1 = 2.40 kg is connected to a second block of mass 𝑚2 = 1.80 kg, as shown in the sketch. When the blocks are released from rest, they move through a distance 𝑑 = 0.500 m, at which point 𝑚2 hits the floor. Given that the coefficient of kinetic friction between 𝑚1 and the horizontal surface is 𝜇𝑘 = 0.450, find the speed of the blocks just before 𝑚2 lands. A 1.75-kg block rests on a ramp of height h. When the block is released, it slides without friction to the bottom of the ramp and then continues across a surface that is frictionless except for a rough patch of width 10.0 cm that has a coefficient of kinetic friction 𝜇𝑘 = 0.640. Find h such that the block's speed after crossing the rough patch is 3.50 m/s. A 1.2-kg block is held at rest against a spring with a force constant 𝑘 = 730 N/m. Initially, the spring is compressed a distance d. When the block is released, it slides across a surface that is frictionless except for a rough patch of width 5.0 cm that has a coefficient of kinetic friction 𝜇𝑘 = 0.44. Find d such that the block's speed after crossing the rough patch is 2.3 m/s. To pass a slow-moving truck, you want your fancy 1.30 × 103 kg car to accelerate from 13.4 m/s (30.0 mi/h) to 17.9 m/s (40.0 mi/h) in 3.00 s. What is the minimum power, in hp, required for this pass? Force and power Each of the four jet engines on an Airbus A380 airliner develops a thrust (a forward force on the airliner) of 322,000 N (72,000 lb). When the airplane is flying at 250 m/s (900 km/h, or roughly 560 mi/h), what horsepower does each engine develop?