A81 cm long brass rod has a diameter of 3 mm. the temperature of one end is 50 degrees higher than the other end. how much heat is conducted in 1.8 mins?

5.14 J

Explanation:

l = 81 cm = 0.81 m

diameter = 3 mm

Radius, r = 1.5 mm = 1.5 x 10^-3 m

Change in temperature, T2 - T1 = 50 degree

t = 1.8 minutes = 1.8 x 60 = 108 s

k = 109 W/mk

Heat transfer = K A (T2 - T1) t / l

H = 109 x 3.14 x 1.5 x 10^-3 x 1.5 x 10^-3 x 50 x 108 / 0.81

H = 5.14 J

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s