in an effort to reach the store before it closed the motorist increase the speed of his car from 20 m per second to 60 meters per second over a four second. What was the car's acceleration

10

Explanation:

Givens

vi = 20 m/s

vf = 60 m/s

t = 4 second.

Formula

a = (vf - vi) / t

a = (60 - 20)/4

a = 40 / 4

a = 10 m/s^2

the displacement produced by the body.  

the amount of force subjected to the body.  

the angle between the direction of force and displacement

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.