When you stretch a spring 13 cm past its natural length, it exerts a force of 21 N. What is the spring constant of this spring?
A. 1.6 N/cm
B. 273 N/cm
C. 0.8 N/cm
D. 13 N/cm

Which of the following harmful chemicals are found in tobacco smoke? a. carbon monoxide b. carbon dioxide c. nicotine b. carbon dioxide d. both a and c

Could someone . i have tried to solve myself but my calculation is off

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?