Question

1. A Constant force pushes an object and speeds it up. The object moves from (6i - 8j + 4k)m to (11i - 5j + 4k)m. The net force acting on the object is (2i + 4j + 5k)N. What is the increase in it's kinetic energy, in J?

So I found in the x direction to be 10 J and in the y direction to be 12 J. I ignored the work in the k direction as the object did not move in that direction. I am confused as to what to do next?

2. Three skiers, (A,B,C) start from rest down a hill with negligible friction and take different routes. One takes a short but steep slope, the second one takes a long but gentle slope and the last one takes a long route over a hill. What is the order of who is going the fastest (highest speed) when they meet at the bottom?

Answer 1

displacement of object -ที่-ที่ r =5i+3j work done by the force on the object W = 10 + 12 W- 22J Now from work energy theorem work done by all forces change in kinetic Energy of object So increase in kinetic energy is 22J

VA If the velocity at the bottom is Now from work energy theorem work done by all forces change in kinetic Energy of object all three starts from rest so initial kinetic energy is zero W, AKE Since h is same for all so their velocity at the bottom is same