Asuspicious-looking man runs as fast as he can along a moving sidewalk from one end to the other, taking 2.90 s. then security agents appear and the man runs as fast as he can back along the sidewalk to his starting point, taking 10.7 s. what is the ratio of the man's running speed to the sidewalk's speed (running speed / sidewalk speed)?

68:39

Explanation:

We have to find the ratio of the man's running speed to the sidewalk's speed.

Let running speed of man=x

Sidewalk's speed=y

When man running  in the same direction as side walk is  moving.

Then, total speed=x+y

Time=2.9 s

When a man running in opposite direction as the side walk is moving.

Then, total speed =x-y

Time =10.7 s

Distance traveled in both cases remain same.

Suppose , d is the distance from one end to another end.

Hence, the ratio of the man's running speed to the sidewalk's speed =68:39

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.