1
Q:

A boy is swinging a ball attached to a string in a horizotal circle. If the string snaps

 A) the ball will travel towards the center of the circle and fall down B) it will continue to travel along a tangent to the circle at the point the ball was at the time of snapping and finally fall down C) it will fall down at the same place where the string breaks D) None of these

Answer:   B) it will continue to travel along a tangent to the circle at the point the ball was at the time of snapping and finally fall down

Explanation:

The centripetal force having been removed the body cannot  execute the curved path

Subject: Physics
Q:

What is the difference between Thermal Energy and Heat Energy?

Energy tranfer takes place either by means of Heat or Work only in Thermodynamics.

Heat :: Heat Energy is defined as Energy that can be transferred due to temperature change.

Whereas

Thermal Energy :: Thermal Energy is the Internal Energy stored in the system maintained at a certain Temperature.

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92
Q:

Rolling friction is caused by ____ from the following?

 A) Non-elastic effects B) Gravity C) Power dissipation D) Buoyancy

Explanation:

Rolling friction or rolling drag is the force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects, that is, not all the energy needed for deformation of the wheel, roadbed, etc... is recovered when the pressure is removed.

Another cause of rolling resistance lies in the slippage between the wheel and the surface, which dissipates energy.

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9 62
Q:

Two metallic plate of equal thickness and coefficient thermal conductivity K1 and K2 put together face to face. A common plate is constructed. What is equivalent K?

 A) K1k2/k1+k2 B) 2k1k2/k1+k2 C) K1+k2/k1k2 D) None

Explanation:

We know that,

The equivalent K =  $\fn_jvn \small \frac{L1+L2}{\frac{L1}{K1}+\frac{L2}{K2}}$

where L1 & L2 are plate1 & Plate2 thicknesses, K1 & K2 are coefficient thermal conductivity of plate1 & Plate2 respectively.

But here L1 = L2 = L (say)

Then K = L+L/(L/K1 + L/K2)  =  $\fn_jvn \small \frac{2K1K2}{K1+K2}$

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6 140
Q:

"Light years" is the unit of _____?

 A) Acceleration B) Distance C) Light Intensity D) Weight

Explanation:

A Light-year is a distance that light travels in the vacuum in one Julian year (365.25 days).

The light-year is a unit of length used to express astronomical distances. It is about 9.5 trillion kilometers or 5.9 trillion miles.

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8 233
Q:

"The Law of Kepler" is related with which among the following ?

 A) Planetary Motion B) Law of Conservation of energy C) Law of Gravitation D) None

Explanation:

Kepler's laws of planetary motion are three scientific laws describing the motion of planets around the Sun.

• Kepler’s three laws of planetary motion can be stated as follows:

(1) All planets move about the Sun in elliptical orbits, having the Sun as one of the foci.

(2) A radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time.

(3) The squares of the sidereal periods (of revolution) of the planets are directly proportional to the cubes of their mean distances from the Sun.