A1000 kg boat is traveling at 90 km/h when its engine is shut off. the magnitude of the frictional force f → k between boat and water is proportional to the speed v of the boat: fk = 70v, where v is in meters per second and fk is in newtons. find the time required for the boat to slow to 45 km/h.

9.9 s

Explanation:

mass (m) = 1000 kg

initial speed (u) = 90 km/h

final speed (v) = 45 km/h

relationship between the speed (v) of the boat and the frictional force (fk) ⇒ fk = 70v

       a =

        (a) = = =

        (a) = =

        t =            

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

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.