Water is used to cool down automobile engines when they get hot. Why is water used as a coolant?
2 answers:
Explanation :
Water is used to cool down automobile engines when they get hot. It is used as a coolant because it has a high heat capacity. It is approximately equal to .
The heat capacity of a substance is defined as the change in temperature due to the addition and removal of heat. Its SI unit is joule per kelvin. It is also an extensive property of matter.
The specific heat of water shows that each gram of water can absorb or release 4.186 joules of heat.
In the case of water, it will soak up a large amount of heat and its do not increase by very large amount.
So, the correct option is (d) "Water has a high heat capacity".
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Answer:
(a) 0.38 m
(b) 2.78 m/s
(c) 0.11 watt
Explanation:
mass, m = 0.3 kg
spring constant, K = 160 N/m
initial compression, d = 12 cm = 01.2 m
initial speed, u = 3 m/s
(a) Let the maximum stretch is y.
Use conservation of energy
Initial potential energy + initial kinetic energy = final potential energy
0.5 x K x d² + 0.5 x m x u² = 0.5 x K x y²
160 x 0.12 x 0.12 + 0.3 x 0.12 x 0.12 = 160 x y²
2.304 + 0.00432 = 160 y²
y = 0.38 m
y = 38 cm
(b) Let v is the maximum speed.
The speed is maximum when the stretch in the spring is zero, so by use of conservation of energy
Initial potential energy + initial kinetic energy = final kinetic energy
0.5 x K x d² + 0.5 x m x u² = 0.5 x m x v²
160 x 0.12 x 0.12 + 0.3 x 0.12 x 0.12 = 0.3 x v²
2.304 + 0.00432 = 0.3 v²
v = 2.78 m/s
(c) The time period of the spring mass system is given by
T = 0.272 second
Energy dissipated per cycle = 0.03 J
Power, P = 0.03 / 0.272 = 0.11 Watt