Two boxes of masses m and 3m are stacked as shown in the figure. the contact between the more massive box and the underlying horizontal surface is smooth (frictionless) and the surface between the boxes is rough. if the upper box does not slide on the lower one, what is the static friction force on the upper box?
a. f.
b. f/2.
c. f/3.
d. f/4 m.

what is the question?

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2