Abrick of 203 × 102 × 57 mm in dimension is being burned in a kiln to 1250°c, and then allowed to cool in a room with ambient air temperature of 30°c and convection heat transfer coefficient of 5 w/m2·k. the brick has properties of rho = 1920 kg/m3, cp = 790 j/kg·k, and k = 0.90 w/m·k. calculate the time required to cool a brick from 1250°c to a temperature difference of 5°c from the ambient air temperature. (round the answer to 2 decimal places.) 7.18 ± 5% hours.

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

b. false

explanation:

suppose a rock in free fall is dropped off a cliff. after falling for 5 seconds, its speed would not be 100 m/s.