IB Physics SL A 3 7 Mechanical Energy Conservation Questions

Practise conserving mechanical energy to calculate speed, height and elastic or gravitational energy when losses are negligible.

Exam points

Apply conservation of mechanical energy when friction and other resistive forces are absent.
Calculate speed, height or elastic-energy changes by relating kinetic, gravitational potential and elastic stores using complete evidence.

[Maximum number: 2]

A student strikes a tennis ball that is initially at rest so that it leaves the racquet at a speed of $64 \mathrm{~m} \mathrm{~s}^{-1}$ . The ball has a mass of 0.058 kg and the contact between the ball and the racquet lasts for 25 ms .

The student strikes the tennis ball at point P . The tennis ball is initially directed at an angle of $7.00^{\circ}$ to the horizontal.

Figure for Question IB Physics SL A 3 7 Mechanical Energy Conservation Questions question 1 — IB Physics SL

The following data are available.

Table for Question IB Physics SL A 3 7 Mechanical Energy Conservation Questions question 1 — IB Physics SL

Determine the speed of the tennis ball as it strikes the ground.

ALTERNATIVE 1

Initial KE+PE= final KE /
$\frac{1}{2} \times 0.058 \times 64^{2}+0.058 \times 9.81 \times 2.80=\frac{1}{2} \times 0.058 \times v^{2}$

ALTERNATIVE 2
$\begin{aligned} & v_{v}=<\sqrt{7.8^{2}+2 \times 9.81 \times 2.8}>=10.8<\mathrm{ms}^{-1} \gg & <v=\sqrt{63.5^{2}+10.8^{2}}> & v=64.4<\mathrm{ms}^{-1} \gg \end{aligned}$

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IB Physics SL A 3 7 Mechanical Energy Conservation Questions question 1