Can someone please help with the middle two questions??

1. explain how you calculate the net force in any direction on the box. 2. suppose an upward force of 15n is added to the box. what will be the net vertical force on the box? 3. what force could be applied to the box to make the net force in the horizontal direction zero? explain. 4. suppose a force of 25n to the right is added to the box. what will be the net force to the right?

Mixing salt in water is an example of physical change

Six pendulums of mass mand length las shown are released from rest at the same angle theta from vertical. rank the pendulums according to the numberof complete cycles of motion each pendulum goes through perminute. a. l= 1m m=2kg b. l= 4m m=1 kg c. l= 2 m m= 2 kg d. l= 1 m m= 4 kg e. l= 2 m m = 4 kg f. l= 4m m = 4kg