Physics 9702 · AS & A Level · Momentum and Newton's laws of motion
Momentum and Newton's laws of motion — practice question
A tiny glass bead with weight $5.4 \times 10^{-5}\,\text{N}$ begins at rest at point A in a vacuum. It then moves in a straight line from A to B through a uniform horizontal electric field, as shown in Fig. 2.1 (not to scale). The electric field strength is $1.3 \times 10^{4}\,\text{V m}^{-1}$. The charge on the bead is $-3.7 \times 10^{-9}\,\text{C}$.
(a)[2]
Explain how two metal plates could be arranged to create the electric field. You do not need to include any numerical values.
(b)[2]
Find the size of the electric force acting on the bead.
(c)[1]
Use your result from (b) and the bead’s weight to show that the resultant force on it is $7.2 \times 10^{-5}\,\text{N}$.
(d)[2]
Explain why the resultant force on the bead of $7.2 \times 10^{-5}\,\text{N}$ remains constant as the bead travels along path AB.
(e(i))[2]
Calculate the size of the bead’s acceleration along path AB.
(e(ii))[2]
The path AB has length $0.58\,\text{m}$. Use your answer in (i) to find the speed of the bead at point B.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The two plates are vertical and separated” …