Physics 9702 · AS & A Level · Momentum and Newton's laws of motion

Momentum and Newton's laws of motion — practice question

An $\alpha$-particle travels in a vacuum in a straight line at a constant speed of $4.1 \times 10^{6}\ \text{m s}^{-1}$. It then enters a uniform electric field at point A, as shown in Fig. 4.1. The $\alpha$-particle keeps moving along the same straight line until the electric field brings it to rest at point B. The deceleration produced by the electric field is $2.7 \times 10^{14}\ \text{m s}^{-2}$.
(a)[1]

State the direction taken by the electric field.

(b)[2]

Calculate the distance between A and B.

(c)[3]

Calculate the magnitude of the electric field strength.

(d)[1]

At $t = 0$, the $\alpha$-particle is at point A. On Fig. 4.2, sketch how the momentum of the $\alpha$-particle changes with time $t$ as it moves from point A to point B. No numerical values are needed.

(e)[1]

State the physical quantity shown by the gradient of the graph in (d).

(f(i))[3]

A $\beta^{-}$ particle enters the electric field along the same initial route as the $\alpha$-particle and with the same initial speed of $4.1 \times 10^{6}\,\text{m s}^{-1}$. Calculate the kinetic energy, in J, of the $\beta^{-}$ particle at point A.

(f(ii))[3]

State and explain how the electric force on the $\beta^{-}$ particle in the electric field differs from the electric force on the $\alpha$-particle in the electric field.

(f(iii))[1]

The $\beta^{-}$ particle is created in the decay of a nucleus. State the name of another lepton created at the same time as the $\beta^{-}$ particle.

Worked solution & mark scheme

This 15-mark question has a full step-by-step worked solution and mark scheme. One marking point: In the direction opposite to the $\alpha$-particle velocity

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