4 March, 04:50

# 3 In a television tube, an electron starting from rest experiences a force of 4.0 * 10-15 N over a distance of 50 cm. The final speed of the electron is (do not worry about relativistic effects) :

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1. 4 March, 05:11
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The final speed of the electron = 2.095*10⁸ m/s

Explanation:

From newton's fundamental equation of dynamics,

F = ma ... Equation 1

Where F = force, m = mass of the electron, a = acceleration of the electron.

making a the subject of the equation,

a = F/m ... Equation 2

Given: F = 4.0*10⁻¹⁵ N,

Constant: m = 9.109*10⁻³¹ kg.

Substituting into equation 2

a = 4.0*10⁻¹⁵/9.109*10⁻³¹

a = 4.39*10¹⁶ m/s².

Using newton's equation of motion,

v² = u²+2as ... Equation 3

Where v = final velocity of the electron, u = initial velocity of the electron, a = acceleration of the electron, s = distance covered by the electron.

Given: u = 0 m/s (at rest), s = 50 cm = 0.5 m, a = 4.39*10¹⁶ m/s²

Substituting into equation 3

v² = 0² + 2 (0.5) (4.39*10¹⁶)

v = √ (4.39*10¹⁶)

v = 2.095*10⁸ m/s

Thus the final speed of the electron = 2.095*10⁸ m/s