Perfectly black body radiates the energy 18 J/s at 300K. Another ordinary body of e=0.8 having same are at 500K will radiate
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(a) 111 J/s (b) 421 J/s (c) 321 J/s (d) […]
A black body is at 727⁰C. It emits energy at a rate which is proportional to
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(a) (1000)⁴ (b) (1000)² (c) (727)⁴ (d) (727)²
Correct Answer:
(1000)⁴
Explanation:
According to Stefan’s law, E […]
The displacement of an object attached to a spring and executing simple harmonic motion is given by x=2×10⁻² cos πt metre. The time at which the maximum speed first occurs is
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(a) […]
One-fourth length of a spring of force constant K is cut away. The force constant of the remaining spring will be
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(a) 3/4 K (b) 4/3 K (c) K (d) 4K
Correct […]
Moment of inertia of a uniform circular disc about a diameter is I. Its moment of inertia about an axis perendicular to its plane and passing throught a point on its rim will be
From a disc of radius R, a concentric circular portion of radius r is cut-out so as to leave an annular disc of mass M. The moment of inertial of this annular disc about the […]
Two cars A and B moving with same speed of 45 km/hr along same direction. If a third car C coming from the opposite direction with a speed of 36 km/hr meets two cars in […]
A car moves from X to Y with a uniform speed v(u) and returns to Y with a uniform speed v(d). The average speed for this round trip is
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(a) √v(u)v(d) (b) […]
A particle is moving in a circle with uniform speed v. In moving from a point to another diametrically opposite point
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(a) The momentum changes by mv (b) The momentum changes by 2mv […]
A cricketer can throw a ball to a maximum horizontal distance of 100 m. With the same effort, he throws the ball vertically upwards. The maximum height attained by the ball is
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