Answer:
1.84 kJ (kilojoules)
Explanation:
A specific heat of 0.46 J/g Cº means that it takes 0.46 Joules of energy to raise the temperature of 1 gram of iron by 1 Cº.
If we want to heat 50 g of iron from 20° C to 100° C, we can make the following calculation:
Heat = (specific heat)*(mass)*(temp change)
Heat = (0.46 J/g Cº)*(50g)*(100° C - 20° C)
[Note how the units cancel to yield just Joules]
Heat = 1840 Joules, or 1.84 kJ
[Note that the number is positive: Energy is added to the system. If we used cold iron to cool 50g of 100° C water, the temperature change would be (Final - Initial) or (20° C - 100° C). The number is -1.84 kJ: the negative means heat was removed from the system (the iron).
Answer: Option (B) is the correct answer.
Explanation:
Convection is defined as a process in which a fluid (liquid or gas) is heated and the cooler liquid (more dense) settles or sinks at the bottom whereas a hotter material (less dense) will rises to the top.
For example, ice being less dense (cooler material) will float in a lake whereas liquid water being more dense will sink at the bottom.
Thus, we can conclude that situation in which convection currents most likely occur is within the water in a lake as ice forms on the top.
Answer:
The angular speed of the sphere at the bottom of the hill is 31.39 rad/s.
Explanation:
It is given that,
Weight of the sphere, W = 240 N
Radius of the sphere, r = 0.2 m
Angle with the horizontal, 
We need to find the angular speed of the sphere at the bottom of the hill if it starts from rest.
As per the law of conservation of energy, the total energy at the top is equal to the energy at the bottom.
Gravitational energy = translational energy + rotational energy
So,
I is the moment of inertia of the sphere, 
Also, 
h is the height of the ramp, 
On solving the above equation we get :
So, the angular speed of the sphere at the bottom of the hill is 31.39 rad/s. Hence, this is the required solution.
