IB Physics SL A.2.19 Newton's Second Law Forms

Practise choosing F = ma for constant mass or resultant force as rate of momentum change, then resolving all external forces before calculating acceleration or mass flow effects.

Exam points

sum external force components before applying Fnet = ma to a constant-mass body
use Fnet = Δp/Δt when momentum changes through impact, radiation pressure or mass flow
derive drag or thrust by finding the mass transferred per second and its velocity change

[Maximum number: 1]

The diagram shows two isolated electrons, X and Y , initially at rest in a vacuum. The initial separation of the electrons is 5.0 mm . The electrons subsequently move apart in the directions shown.

Figure for Question A.2.19—Newton’s second law forms question 1 — IB Physics SL

Calculate the initial acceleration of one electron due to the force in (c)(i).

$1.0 \times 10^{7} \mathrm{~ms}^{-2}\left(9.9 \times 10^{6} \mathrm{~ms}^{-2}\right.$ if $9 \times 10^{-24} \mathrm{~N}$ used );

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A.2.19—Newton’s second law forms question 1