Problems 74 and 75 are paired. 74. In the early part of the 20th century, Sir Jo

Question

Problems 74 and 75 are paired. 74. In the early part of the 20th century, Sir Joseph J. Thomson (dis- coverer of the electron) proposed a "plum pudding" model of the atom. He believed that the positive charge of the atom was spread out like a pudding and that the negative charges (electrons) were embedded in the pudding like plums. His student Ernest Rutherford performed an experiment in 1911 that disproved the plum pudding model. Rutherford fired a beam of alpha particles (helium nuclei) at a thin metal sheet. Because alpha particles are positive, the plum pudding model predicted that they should only

Explanation / Answer

given, initial speed of alpha particle, u = 2*10^7 m/s

mass, m = 6.7*10^-27 kg

a. for an elastic collision with an atomic nucleus that is too heavy, it will not move

hence for elastic collision, KE of the system must be conserved

hence final speed of the alpha particle will be u = 2*10^7 m/s

b. mass of gold nucleus , M = 196.96*1.6*10^-27 kg

initial velocity of alpha particle = u in x direction

final velocity of alpha particle = u in y direction

let final velocity of gold nucleus be v in vecotr form

then fromconservation of momentum

6.7*10^-27*2*10^7 i = 6.7*10^-27*2*10^7j + 196.96*1.6810^-27*v

6.7*2*10^7 i = 6.7*2*10^7j + 196.96*1.68*v

v = 404964.991(i - j) m/s

|v| = 572706.983 m/s

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

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