A librarian lifts a box of books of mass 6.0 kg from the floor onto a shelf, raising it through a height of 1.5 m. Take gravitational field strength g = 10 N/kg. What is the increase in the gravitational potential energy store of the box of books?

Answer: D. Step 1: Recall the equation for gravitational potential energy The change in gravitational potential energy store is: Ep = mg h Step 2: Substitute the values Ep = 6.0 kg × 10 N/kg × 1.5 m Step 3: Work out the answer Ep = 60 N × 1.5 m = 90…

Energy, Work and Power: Question 6

Syllabus 1.7.1

Multiple choice Core 1 mark

A librarian lifts a box of books of mass $6.0\text{ kg}$ from the floor onto a shelf, raising it through a height of $1.5\text{ m}$ . Take gravitational field strength $g = 10\text{ N/kg}$ . What is the increase in the gravitational potential energy store of the box of books?

Show worked solution Hide worked solution

Step 1: Recall the equation for gravitational potential energy

The change in gravitational potential energy store is:

$\Delta E_p = mg\Delta h$

Step 2: Substitute the values

$\Delta E_p = 6.0\text{ kg} \times 10\text{ N/kg} \times 1.5\text{ m}$

Step 3: Work out the answer

$\Delta E_p = 60\text{ N} \times 1.5\text{ m} = 90\text{ J}$

Why the other options are wrong

Option	How it arises	Error
$9.0\text{ J}$	$6.0 \times 1.5$	Left out $g$ entirely
$60\text{ J}$	$6.0 \times 10$	Left out the height, gave the weight instead
$88.2\text{ J}$	$6.0 \times 9.8 \times 1.5$	Used $g = 9.8\text{ N/kg}$ instead of the given $g = 10\text{ N/kg}$

Final answers

Increase in gravitational potential energy $= \boxed{90\text{ J}}$ , option D