19. A CONSTANT force acts on an object and increases its kinetic energy, by 24 J

Question

19. A CONSTANT force acts on an object and increases its kinetic energy, by 24 J. The object moves from (7i-8j+4k)m to (11i-5j+4k) m. The net force acting on the object is equal to (Fxi4j+5 k) N. What is Fx, in N. b.-4 c. 4 d. 3 20. As shown in the figure, a block is pushed up against a vertical wall by a force 20 N. The force is at an angle of 40 degrees from horizontal. The coefficient of static friction between the block and the wall is 0.50. Find the maximum mass, in kg, that the force can prevent from sliding down. a. Infinite b. 0.92 c. 2.1 d. 0.52 e. 10

Explanation / Answer

By work energy theorem,

Net work done by the conservative forces on the body= change in kinetic energy

So work done =24J

Now also

Work done is

F.s

So

W=F(11-7)+4(-5-(-8))+5(4-4)

24=4F+12

4F=12

F=3

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