Figure 10 shows a small steel ball held at a height, h, above the ground - Edexcel - GCSE Physics - Question 7 - 2021 - Paper 1

One reason could be the students' reaction time while starting and stopping the stopwatch, which can affect the recorded time. This delay would lead to a longer measured time compared to the calculated time.

The students could use light gates to accurately measure the time as the ball passes through, reducing human reaction time errors.

To calculate the force exerted by the floor on the box, we can use the formula:

$\text{Force} = \frac{\text{Change in momentum}}{\text{Time}}$

The change in momentum is 8.7 kg m/s, and the time taken to come to rest is 0.355 s. Therefore:

$\text{Force} = \frac{8.7}{0.355} \approx 24.57 \, \text{N} \approx 25 \, \text{N}$

The magnitude of the force exerted by the box on the floor is 25 N, and the direction is upwards (opposite to the direction of the force exerted by the floor on the box).

To find the mass of the ball, we can use the formula for momentum:

$ext{Momentum} = m \times v$

Where:

• Momentum = 0.40 kg m/s
• Velocity at S (just before it falls) = 8.7 m/s

Rearranging the formula gives:

$m = \frac{\text{Momentum}}{v} = \frac{0.40}{8.7} \approx 0.046 \, \text{kg}$