Question 4891:

A nail is pulled from a wall with a string tied to the nail. If the string is inclined at an angle of \(30^{\circ}\) to the wall and the tension in the string is \(50 N\), the effective force used in pulling the nail is ____________

A. 25 N
B. \(25 \sqrt{3} N\)
C. 50 N
D. \(50 \sqrt{3} N\)

Question 4892:

If \(M\) and \(R\) are the mass and radius of the earth respectively and \(G\) is the universal gravitational constant, the earth's gravitation potential at an altitude \(H\) above the ground level is ____________

A. \(-\frac{G M}{H}\)
B. \(-\frac{G M}{(R+H)}\)
C. \(-\frac{G M}{2 H}\)
D. \(-\frac{G M}{(R-H)}\)

Question 4893:

Which of the following statements is not true?

A. As the slope of an inclined plane increases, the velocity ratio decreases.
B. The efficiency of an inclined plane decreases as the slope increases.
C. The effort required to push a given load up an inclined plane increases as the slope increases
D. The mechanical advantage of smooth inclined plane depends on the ratio of the length to the height of the plane.

Question 4894:

The ice and steam points of a thermometer are \(20 mm\) and \(100 mm\) respectively:
A temperature of \(75^{\circ} C\) corresponds to \(Y mm\) on the thermometer. What is \(Y\) ?

A. \(100 mm\)
B. \(70 mm\)
C. \(80 mm\)
D. \(60 mm\)

Question 4895:

An electric kettle with negligible heat capacity is rated at \(2000 W\), if \(2.0 kg\) of water is put in it, how long will take the temperature of water to rise from \(20^{\circ} C\) to \(100^{\circ} C\) ? [Specific heat capacity of water
\(\left.=4200 Jkg ^{-1} K ^{-1}\right]\)

A. \(336 s\)
B. \(240 s\)
C. \(168 s\)
D. \(84 s\)