A8.1-kg rock and a 8.4 × 10-4-kg pebble are held near the surface of the earth. (a) determine the magnitude of the gravitational force exerted on each by the earth. (b) calculate the magnitude of the acceleration of each object when released.

a). Gravitational force exerted by the Earth = (mass) x (grav acceleration)

-- 8.1 kg rock:  (8.1 kg) x (9.81 m/s²)  =  79.46 Newtons

-- 8.4 x 10⁻⁴ kg pebble: (8.4 x 10⁻⁴ kg) x (9.81 m/s²)  =  0.00824 Newton

b). Acceleration following release.

Near the Earth's surface, and neglecting air resistance, all objects have the same acceleration when released.  If air resistance can be neglected, then a feather, the 0.00084 kg pebble, the neckline of an evening gown, a school-bus, and the battleship USS Midway, if dropped together, will fall together and hit the ground at the same time.  

answer:   you might love summer weather, but you don’t want it to feel like the sun is inside your car. but a hot car that just won’t seem to cool down might be a bigger of a problem than you think. your car relies on being at the right temperature.

explanation:

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.