Question detail
A 2 kg object is lifted to a height of 15 m. Calculate the gravitational potential energy gained. Use g = 9.8 N/kg.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Energy changes in a system, and the ways energy is stored before and after such changes
Question
A 2 kg object is lifted to a height of 15 m. Calculate the gravitational potential energy gained. Use g = 9.8 N/kg.
Answer
294 J
Explanation
This answer is strong as it correctly utilizes the gravitational potential energy formula, showing the relationship between mass, height, and gravitational field strength. This answer is linked to Changes in energy because it applies the learning objective: Calculate gravitational potential energy gained by an object raised above ground level.. It shows the Physics relationship clearly and keeps energy, power, work done and efficiency terms distinct where they appear.
Common mistake
Confusing gravitational field strength with acceleration due to gravity
Students often use g = 9.8 m s⁻² as the gravitational field strength in the formula Ep = m g h, but g is the acceleration due to gravity, not the field strength. They then treat g as a unitless constant and ignore that the field strength can vary with location or be given explicitly in the problem.
Remind students that the gravitational field strength (g) is the force per unit mass and has units of N kg⁻¹ (or m s⁻²). In the formula Ep = m g h, g is the field strength, so it must be supplied or calculated from the local value of g. If the problem states the field strength directly, use that value; if it only gives the acceleration due to gravity, treat it as the field strength for the calculation. Always keep the units consistent: m (kg) × g (N kg⁻¹) × h (m) = J.
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