An engineer measures the useful power output of an escalator in raising a stationary passenger of mass 75 kg.
The table shows the correct measurements and the values used by the engineer.
| quantity | correct measurement | value used by the engineer |
|---|---|---|
| distance | vertical rise of 3.6 m | distance along the escalator of 7.2 m |
| journey time | 20.0 s | 19.5 s |
Use g=10 N/kgg = 10\ \mathrm{N/kg}g=10 N/kg.
Calculate the percentage by which the engineer's value for the useful power differs from the actual useful power. State whether the engineer's value is higher or lower.