This question is about energy changes - Edexcel - GCSE Physics Combined Science - Question 4 - 2021 - Paper 1

As the person comes to rest after the water slide, the gravitational potential energy they had at the top is converted into kinetic energy as they slide down. Once they reach the bottom and stop, this kinetic energy is dissipated mainly due to friction and air resistance. Some energy is also transferred to the water and the slide itself as thermal energy, thus reducing their kinetic energy to zero.

To calculate the work done against the force of friction, the distance moved in the direction of the applied force should be considered. In this case, the distance along the slope (hypotenuse) of 6.3 m should be used, as friction acts along the slope during the push.

First, convert the mass of the tennis ball from grams to kilograms:

$58 ext{ g} = 0.058 ext{ kg}$

To calculate the kinetic energy (KE), we use the formula:

$KE = \frac{1}{2} \times m \times v^2$

Substituting in the values:

$KE = \frac{1}{2} \times 0.058 \text{ kg} \times (28 ext{ m/s})^2$

Calculating this gives:

$KE = \frac{1}{2} \times 0.058 \times 784 = 22.736 ext{ J}$

Rounding this value, the kinetic energy is approximately 23 J.