Mary applies a force of 73 N to push a box with an acceleration of 0.48 m/s^2. When she increases the pushing force to 84 N, the box's acceleration changes to 0.64 m/s^2. There is a constant friction force present between the floor and the box. Required:
a. What is the mass of the box?
b. What is the coefficient of kinetic friction between the floor and the box?

Explanation:

Mary applies a force of 73 N to create an acceleration of

When She increases force to 84 N, it creates an acceleration of

Friction opposes the motion of box

Subtract (i) from (ii)

Therefore friction is

Here, friction is kinetic friction which is given by

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27