A 3.0-kg mass is dropped from the edge of a 50 m tall building with an initial s

Question

A 3.0-kg mass is dropped from the edge of a 50 m tall building with an initial speed of zero. The mass strikes the ground with a downward velocity of 25 m/s. Find the change in mechanical energy of the mass caused by air resistance between the point where it is dropped and the point where it strikes the ground? - 0.46 kJ - 0.53 kJ - 0.61 kJ - 0.38 kJ - 0.81 kJ The escape speed from the surface of the Earth is 11.2 km/s. Estimate the escape speed for a spacecraft from the surface Moon. The Moon has a mass 1/81 that of Earth and a radius 0.25 that of Earth. 2.5 km/s 4.0 km/s 5.6 km/s 8.7 km/s Constants: G = 6.67 times 10^-11 N m^2/kg^2 mu_0 = 1.26 times 10^-6 T m/A. e - = 1.60 times10^-19 C epsilon_0 = 8.85 times 10^-12 M_E = 5.98 times 10^24 kg R_E = 6.38times 10^6 m k = 8.99 times 10^9 Nm^2/C^2

Explanation / Answer

11. mechanical energy = kinetic energy + potential energy

= 1/2 x mv2 + mgh

M.E at top = 1/2 x 3 x 0 + 3 x 9.8 x 50

= 0 + 1470

= 1470 J

M.E at bottom = 1/2 x 3 x 252    + 3x 9.8x0

=937.5J

change in M.E. = M.E at bottom - M.E. at top

= 937.5 J - 1470 J

= -532.5 J

= - 0.53 kJ

option B is the correct answer

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.