Physics Answers

X-ray from a certain cobalt target tube are composed of the strong 𝐾 series

of Cobalt and weak 𝐾 lines due to impurities. The wavelengths of 𝐾𝛼 are

1.785𝐴

𝑜

for Cobalt and 2.285𝐴

𝑜

and 1.537𝐴

𝑜

for impurities. (a) What

elements are they? [For the 𝐾-series, a=1 in Moseley’s law]

 A long jumper moving horizontally with a speed of 5.3 m/s has a kinetic energy of 235 J. Calculate the mass of the jumper.

A planet orbiting a distant star has a radius 3.24 × 106 𝑚. The escape speed for an object launched from this planet’s surface is 7.65 × 103 𝑚/𝑠. What is the acceleration due to gravity at the surface of the planet?

Rhea, one of Saturn’s moons, has a radius of 764 𝑘𝑚 and an acceleration due to the gravity of 0.265 𝑚/𝑠 2 at its surface. Calculate its mass and average density. 

At what distance above the surface of the earth is the acceleration due to the earth’s gravity 0.980 𝑚/𝑠 2 if the acceleration due to gravity at the surface has a magnitude of 9.80 𝑚/𝑠 2 ?

Three uniform spheres are fixed at the positions shown in Figure 90. (a) What are the magnitude and direction of the force on a 0.0150-𝑘𝑔 particle placed at 𝑃? (b) If the spheres are in deep outer space and a 0.0150-𝑘𝑔 particle is released from rest 300 𝑚 from the origin along a line 45 below the – 𝑥-axis, what will the particle’s speed be when it reaches the origin?

Two uniform spheres, each of mass 0.260 𝑘𝑔, are fixed at points 𝐴 and 𝐵 (Figure 89). Find the magnitude and direction of the initial acceleration of a uniform sphere with mass 0.010 𝑘𝑔 if released from rest at point 𝑃 and acted on only by forces of gravitational attraction of the spheres at 𝐴 and 𝐵.

An 8.00-𝑘𝑔 point mass and a 12.0-𝑘𝑔 point mass are held in place 50.0 𝑐𝑚 apart. A particle of mass 𝑚 is released from a point between the two masses 20.0 𝑐𝑚 from the 8.00-𝑘𝑔 mass along the line connecting the two fixed masses. Find the magnitude and direction of the acceleration of the particle. 

A typical adult human has a mass of about 70 𝑘𝑔. (a) What force does a full moon exert on such a human when it is directly overhead with its center 378,000 𝑘𝑚 away? (b) Compare this force with the force exerted on the human by the earth.

Two uniform spheres, each with mass 𝑀 and radius 𝑅, touch each other. What is the magnitude of their gravitational force of attraction?