#### Transcript An 875 kg car speeds from 22 m/s to 44 m/s. What were its initial and

An 875 kg car speeds from 22 m/s to 44 m/s. What were its initial and final energies? If you lift a 2 kg textbook from the floor to a shelf 2.1 m above the floor. What is PEg relative to the floor? Relative to your head if you are 1.65 m tall? A slinky is stretched a distance of 3 m. If the amount of energy in the spring is 310 J, what is the spring constant? What would be the velocity of a 0.500 g raindrop if it fell 0.250 km to the ground without any resistance provided by air? A 100.0 g arrow is pulled back 30.0 cm against a bowstring. If the spring constant of the bowstring is 1250 N/m, at what speed will the arrow leave the bow? Suppose a squirrel sitting on top of a redwood tree drops a 20 g walnut. If the speed of the falling walnut at the moment it is 50 m above the ground is 42.7 m/s, how tall is the tree? Suppose a coin is dropped from a hot air balloon at a height of 3150 m. How high above the ground is the coin when its speed is 60.0 m/s? Block whose mass is 5.7 kg slides on a horizontal frictionless tabletop with a constant velocity of 1.2 m/s. It is momentarily brought to rest as it compresses a spring in its path. By what distance is the spring compressed? The spring constant is 1500 N/m. v=0 A 0.4 kg ball starts from rest at point A and slides along a frictionless curved wire. What is the velocity at point B? Point C?A C 5m 2m B A 2000 kg roller coaster that has a vertical drop of 68.6 m, is designed so that the speed of the cars at the end of this drop is 35.6 m/s. Assume the cars are at rest at the start of the drop. What amount of the initial mechanical energy is dissipated by friction? = 97 N = 20 N =5m = 147 N An applied force of 92 N is exerted horizontally on an 18 kg box of books. The coefficient of kinetic friction is 0.35. If the box is initially at rest, what is net work done after has been moved 7.6 m? A wagon is pulled rightward a horizontal distance of 15.0 m. The handle of the wagon makes an angle of 20.0° with the horizontal, and the girl exerts a force of 35.0 N on the handle. Friction provides a force of 24.0 N. Find the net work that is done on the wagon. A force of 102 N moves the 800 kg boat 0.90 km. Assume A 2.00 × 102 kg iceboat is propelled across the horizontal that frictional forces are surface of a frozen lake by the wind. The wind negligible that exertsand a constant force of 4.00 × the boat starts from rest. What is the boat’s final speed? A hockey puck with an initial speed of 8.0 m/s coasts 45 m to a stop across the ice. If the force of friction on the puck has a magnitude of 0.12 N, what is the puck’s mass? A crane hoist lifts a load of 1000 kg a vertical distance of 25 m in 9.0 s, at a constant velocity. What is the power of the Crane? A runner exerts a force of 334 N against the ground and is exerting 2100 W of power. How long does it take the runner to run a distance of 50.0 m? A railway car with a mass of 8500 kg and a velocity of 4.5 m/s to the right collides in-elastically with a railway car with a mass of 9800 kg and a velocity of 3.9 m/s to the left. What is the final velocity of the combined cars? How much KE was lost? KE = ? vf= ? Before Colliding Trains (in-elastic) After m1 = 18,000 kg v1i = 8 m/s m2 = 24,000 kg v2i = 0 m/s A 5 kg ball moves to the right at 20 m/s and elastically collides with a 10 kg ball that is initially at rest. After the collision the 5 kg ball moves to the left at 6.68 m/s. What is the velocity of the 10 kg ball after the collision? Check your answer using conservation of KE. A 10 kg ball moving to the right elastically collides with a 15 kg ball that is moving to the left at 30 m/s. After the collision, the 10 kg ball moves to the left at 40 m/s and the 15 kg ball moves to the right at 10 m/s. What was the initial velocity of the 10 kg ball? Check your answer using cons. of KE