Class 9 – Practice Level 3 – Gravitation – Set 1 Leave a Comment / By Gulam Hamza / July 9, 2024 Class 9 - Practice Level 3 - Gravitation - Set 1 Total questions: 15 1. Two spherical objects have masses of 30 kg and 45 kg, and their centers are 0.5 meters apart. Calculate the gravitational force between them. $\displaystyle \left( {Use\text{ }G\text{ }=\text{ }6.67\times {{{10}}^{{-11}}}\,N{{m}^{2}}/k{{g}^{2}}} \right)$ Topic: Gravitational Force Between Two Spheres $ \displaystyle {Gravitational\text{ }force:\text{ }4.00\times {{{10}}^{{-9}}}\,N}$ $\displaystyle {Gravitational\text{ }force:\text{ }3.60\times {{{10}}^{{-8}}}\,N}$ $ \displaystyle {Gravitational\text{ }force:\text{ }7.20\times {{{10}}^{{-8}}}\,N}$ $ \displaystyle {Gravitational\text{ }force:\text{ }9.00\times {{{10}}^{{-9}}}\,N}$ None 2. Calculate the gravitational potential energy of a system of two 20 kg masses separated by a distance of 2 meters.$\displaystyle \left( {Use\text{ }G\text{ }=\text{ }6.67\times {{{10}}^{{-11}}}\,N{{m}^{2}}/k{{g}^{2}}} \right)$ Topic: Gravitational Potential Energy in Two-Body System $ \displaystyle {\text{Potential energy}:\text{ }-1.33\times {{{10}}^{{-8}}}\,J}$ $ \displaystyle {\text{Potential energy}:\text{ }-1.33\times {{{10}}^{{-9}}}\,J}$ $ \displaystyle {\text{Potential energy}:\text{ }-2.67\times {{{10}}^{{-8}}}\,J}$ $ \displaystyle {\text{Potential energy}:\text{ }-2.67\times {{{10}}^{{-9}}}\,J}$ None 3. Calculate the orbital speed of a satellite orbiting the Earth at an altitude of 800 km. $ \displaystyle \left( {Radius\text{ }of\text{ }Earth\text{ }R\text{ }=\text{ }6400\,km,\text{ }g\text{ }=\text{ }9.8\,m/{{s}^{2}}} \right)$ Topic: Orbital Speed Calculation Orbital speed: 7.5 km/s Orbital speed: 7.8 km/s Orbital speed: 8.0 km/s Orbital speed: 8.3 km/s None 4. An object is dropped from a height of 80 meters. Assuming no air resistance, calculate the time taken to reach the ground.$ \displaystyle \left( {Use\text{ }g\text{ }=\text{ }9.8\,m/{{s}^{2}}} \right)$ Topic: Free Fall from Height Calculation Time: 3.5 s Time: 4.0 s Time: 4.5 s Time: 5.0 s None 5. Calculate the gravitational field strength at a distance of 3000 km from the Earth's surface. $ \displaystyle \left( {Radius\text{ }of\text{ }Earth\text{ }R\text{ }=\text{ }6400\,km,\text{ }g\text{ }=\text{ }9.8\,m/{{s}^{2}}} \right)$ Topic: Gravitational Field Strength Calculation Field strength: 4.0 N/kg Field strength: 5.0 N/kg Field strength: 6.0 N/kg Field strength: 7.0 N/kg None 6. Calculate the energy required to move a 10 kg mass from the Earth's surface to an altitude of 200 km. $ \displaystyle \left( {Radius\text{ }of\text{ }Earth\text{ }R\text{ }=\text{ }6400\,km,\text{ }g=9.8\,m/{{s}^{2}}} \right)$ Topic: Energy Required to Move Mass Energy: 588 J Energy: 548 J Energy: 612 J Energy: 408 J None 7. If the mass of one object is tripled and the distance between two objects is halved, how does the gravitational force between them change? Topic: Gravitational Force and Masses It becomes 6 times It becomes 12 times It becomes 24 times It becomes 36 times None 8. Calculate the work done in lifting a 5 kg object to a height of 10 meters. $ \displaystyle \left( {Use\text{ }g\text{ }=\text{ }9.8\,m/{{s}^{2}}} \right)$ Topic: Work Done Against Gravity Work done: 245 J Work done: 450 J Work done: 490 J Work done: 980 J None 9. A planet orbits the Sun at an average distance of 1 AU (astronomical unit). If another planet orbits at 4 AU, what is the ratio of their orbital periods? Topic: Kepler's Third Law Ratio: 2:1 Ratio: 4:1 Ratio: 8:1 Ratio: 16:1 None 10. Calculate the gravitational potential energy of a 2 kg mass at a height of 50 meters above the ground.$ \displaystyle \left( {Use\text{ }g=9.8\,m/{{s}^{2}}} \right)$ Topic: Gravitational Potential Energy at Height Potential energy: 490 J Potential energy: 780 J Potential energy: 980 J Potential energy: 1960 J None 11. Calculate the net gravitational force on a 5 kg mass placed at the midpoint between two 10 kg masses separated by 1 meter.$ \displaystyle \left( {Use\text{ }G\text{ }=\text{ }6.67\times {{{10}}^{{-11}}}\,N{{m}^{2}}/k{{g}^{2}}} \right)$ Topic: Gravitational Potential Energy in Two-Body System Net force: 10 N Net force: 5 N Net force: 50 N Net force: 0 N None 12. Calculate the escape velocity from the surface of the Moon where the radius of the Moon is $ \displaystyle 1.74\times {{10}^{6}}\,m\text{ }and\text{ }g\text{ }=\text{ }1.6\,m/{{s}^{2}}$ Topic: Escape Velocity from Moon Escape velocity: 1.2 km/s Escape velocity: 1.6 km/s Escape velocity: 2.4 km/s Escape velocity: 3.2 km/s None 13. Using Kepler’s third law, determine the orbital period of a planet that is 5 AU away from the Sun if Earth's orbital period is 1 year. Topic: Kepler's Laws Application Orbital period: 5 years Orbital period: 8 years Orbital period: 11 years Orbital period: 25 years None 14. If the distance between two masses is increased by a factor of 3, how does the gravitational force between them change? Topic: Gravitational Force and Varying Distances It becomes one-third It becomes one-ninth It becomes one-twentieth It becomes one-thirtieth None 15. Newton’s law of gravitation applies to Topic: Newton's Law of Gravitation Solar system Small bodies only Large bodies only All bodies irrespective of their size None 1 out of 15 Time's up
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