Chapter 7: Problem 61
Calculate the ratio \(m_{0} / m\) for a rocket if it is to escape from the earth. Given escape velocity \(=11.2 \mathrm{~km} / \mathrm{s}\) and exhaust speed of gases is \(2 \mathrm{~km} / \mathrm{s}\).
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Chapter 7: Problem 61
Calculate the ratio \(m_{0} / m\) for a rocket if it is to escape from the earth. Given escape velocity \(=11.2 \mathrm{~km} / \mathrm{s}\) and exhaust speed of gases is \(2 \mathrm{~km} / \mathrm{s}\).
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A particle is placed in a field characterized by a value of gravitational potential given by \(V=-k x y\), where \(k\) is a constant. If \(\vec{E}_{g}\) is the gravitational field then, (A) \(\vec{E}_{g}=k(x \hat{i}+y \hat{j})\) and is conservative in nature. (B) \(\vec{E}_{g}=k(y \hat{i}+x \hat{j})\) and is conservative in nature. (C) \(\vec{E}_{g}=k(x \hat{i}+y \hat{j})\) and is non-conservative in nature (D) \(\vec{E}_{g}=k(y \hat{i}+x \hat{j})\) and is non-conservative in nature.
Two bodies of masses \(m\) and \(4 m\) are placed at a distance \(r .\) The gravitational potential at a point on the line joining them where the gravitational field is zero is (A) \(-\frac{4 G m}{r}\) (B) \(-\frac{6 G m}{r}\) (C) \(-\frac{9 G m}{r}\) (D) Zero
A solid sphere of uniform density and radius 4 units is located with its centre at the origin \(O\) of co-ordinates. Two spheres of equal radii 1 units, with their centres at \(A(-2,0,0)\) and \(B(2,0,0)\) respectively, are taken out of the solid leaving behind spherical cavities as shown in Fig. 7.12. Then (A) the gravitational field due to this object at the origin is zero. (B) the gravitational field at the point \(B(2,0,0)\) is zero. (C) the gravitational potential is same at all points on the circle \(y^{2}+z^{2}=36\) (D) the gravitational potential is same at all points on the circle \(y^{2}+z^{2}=4\)
Three planets of same density have radii \(R_{1}, R_{2}\) and \(R_{3}\) such that \(R_{1}=2 R_{2}=3 R_{3}\). The gravitational field at their respective surfaces are \(g_{1}, g_{2}\) and \(g_{3}\) and escape velocities from their surfaces are \(v_{1}, v_{2}\) and \(v_{3}\) respectively, then (A) \(g_{1} / g_{2}=2\) (B) \(g_{1} / g_{3}=3\) (C) \(v_{1} / v_{2}=1 / 4\) (D) \(v_{1} / v_{3}=3\)
The escape velocity for a body projected vertically upwards from the surface of earth is \(11 \mathrm{~km} / \mathrm{s}\). If the body is projected at an angle of \(45^{\circ}\) with the vertical, the escape velocity will be (A) \(11 \sqrt{2} \mathrm{~km} / \mathrm{s}\) (B) \(22 \mathrm{~km} / \mathrm{s}\) (C) \(11 \mathrm{~km} / \mathrm{s}\) (D) \(\frac{11}{\sqrt{2}} \mathrm{~m} / \mathrm{s}\)
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