Answer:
option (c)
Explanation:
90% of the body is submerged in water.
Now it is immersed in an unknown liquid whose density is less than the density of water.
Buoyant force acting on the body depends on the volume immersed, density of liquid and gravity.
As the density of liquid is less than the density of water, so the buoyant force acting on the body by the unknown liquid is less than water. So it is submerged less than 90% in this liquid.
Kinetic energy = (1/2) (mass) x (speed)²
At 7.5 m/s, the object's KE is (1/2) (7.5) (7.5)² = 210.9375 joules
At 11.5 m/s, the object's KE is (1/2) (7.5) (11.5)² = 495.9375 joules
The additional energy needed to speed the object up from 7.5 m/s
to 11.5 m/s is (495.9375 - 210.9375) = <em>285 joules</em>.
That energy has to come from somewhere. Without friction, that's exactly
the amount of work that must be done to the object in order to raise its
speed by that much.
Recall the definition of the cross product with respect to the unit vectors:
i × i = j × j = k × k = 0
i × j = k
j × k = i
k × i = j
and that the product is anticommutative, so that for any two vectors u and v, we have u × v = - (v × u). (This essentially takes care of part (b).)
Now, given a = 8i + j - 2k and b = 5i - 3j + k, we have
a × b = (8i + j - 2k) × (5i - 3j + k)
a × b = 40 (i × i) + 5 (j × i) - 10 (k × i)
… … … … - 24 (i × j) - 3 (j × j) + 6 (k × j)
… … … … + 8 (i × k) + (j × k) - 2 (k × k)
a × b = - 5 (i × j) - 10 (k × i) - 24 (i × j) - 6 (j × k) - 8 (k × i) + (j × k)
a × b = - 5k - 10j - 24k - 6i - 8j + i
a × b = -5i - 18j - 29k
The refrigerator's coefficient of performance is 6.
The heat extracted from the cold reservoir Q cold (i.e., inside a refrigerator) divided by the work W required to remove the heat is known as the coefficient of performance, or COP, of a refrigerator (i.e., the work done by the compressor). The required inside temperature and the outside temperature have a significant impact on the COP.
As the inside temperature of the refrigerator decreases, its coefficient of performance decreases. The coefficient of performance (COP) of refrigeration is always more than 1.
The heat produced in the cold compartment, H = 780.0 J
Work done in ideal refrigerator, W = 130.0 J
Refrigerator's coefficient of performance = H/W
= 780/130
= 6
Therefore, the refrigerator's coefficient of performance is 6.
Energy conservation requires the exhaust heat to be = 780 + 130
= 910 J
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Energy and Work have the same unit of measurement which is Joules in SI units.
Explanation:
- A Joule of Work is said to be done on an object when energy is transferred to that particular object.
- If two objects are involved, when one object transfers energy onto the second, a joule of work is said to be done by the first object.
- Work is also the application of force on an object over a distance. So Work = Force × Displacement
- Energy is neither created nor destroyed. It is in 2 forms - kinetic and potential.
- Kinetic energy is defined as the energy of a moving object while potential energy is known as the energy that is stored within an object.
- Kinetic Energy = 1/2 × mass × (velocity)²
- Potential Energy = mass × acceleration due to gravity × height
- Both energy and work are measured in Joules.
