Initial velocity (u) = 90km/hr = 90/3.6 m/s = 25m/s
final velocity (v) = 18km/hr = 18/3.6 m/s = 5m/s
acceleration = (v-u)/t = (5-25)/4 = -5 m/s2
change in momentum = m(v-u) = 1200(5-25) = -24000 kg•m/s
F = ma = 1200 x -5 = -6000 N
Answer:
f=-1380N
Explanation:
A karate master wants to break a board by hitting the board swiftly with his hand. The master's hand has a mass of 0.30 kg, and as it strikes the board, his hand has a velocity of 23.3 m/s. The master contacts the board for 0.0050 seconds
.the concluding part to the question should be
What is the impact force (impulse) on the board?
solution
from the Newton's second law of motion which states that
the rate of change in momentum is directly proportional to the force applied
f=m(v-u)/t
f=0.3(0-23.3)/0.005
f=-1380N
f=force impact
m=mass of the karates master's hand
t=time for the impact
v=0m/s final velocity
u=initial velocity
You need an additional point of data here: the enthalpy of fusion, or conversely the enthalpy of melting (they differ only by their sign). For water (or ice) that value is gotten from sources such as the internet
<span>ΔH°(fus) = 6.01 kJ/mole </span>
<span>Since you have 35 000g, how many moles do you have? </span>
<span>Moles H2O = 35000 g/(18.015 g/mole) = 1942.8 moles</span>
<span>So, take that ΔH°(fus) in kJ/mole, multiply by the number of moles, and there ya go!
</span>
6.01 x 1942.8 = 11,676 kJ of energy is released
Hope I helped!! xx