Question

A box of weight 100 N is lifted to a height of 10 m above ground. How much potential energy will be stored in the box?

9800 J
1000 J
2000 J
none of the above

Answer 1

Given

• Weight of a box = 100 N
• Height above the ground = 10 m

To Find

• Potential Energy stored in the box

Solution

• Potential Energy is equal to the product of the mass, the acceleration and the height of the body (Pe = mgh) so we shall first find the mass of the body and then simple substitution will give us our answer
• Note that we here use the gravitational acceleration as 10 m/s²

✭ Mass of the Body :

→ W = ma

→ 100 = m × 10

→ 100/10 = m

→ Mass = 10 kg

━━━━━━━━━━━━━━

✭ Potential Energy :

→ Pe = mgh

• m = Mass = 10 kg
• g = Gravitational Acceleration = 10 m/s²
• h = Height = 10 m

→ Pe = 10 × 10 × 10

→ Pe = 1000 J

∴ The answer is Option B

Answer 2

$\large{\underline{\underline{\sf{ \maltese \: {Given:-}}}}}$

• Weight = 100 N
• Height = 10 m

$\large{\underline{\underline{\sf{ \maltese \: {To \: find:-}}}}}$

• Potential energy = ?

$\large{\underline{\underline{\sf{ \maltese \: {Solution:-}}}}}$

➊ We know that:–

$\qquad \bull \bf \: {Weight = Mass \times Acceleration }$

$\qquad \quad {:} \longrightarrow\sf \: {100 = mass \times 10 }$

$\qquad \quad {:} \longrightarrow\sf \: { \dfrac{100}{10} = mass }$

$\qquad \quad {:} \longrightarrow\sf \: { mass = \cancel\dfrac{100}{10} }$

$\qquad \quad {:} \longrightarrow\sf \: \underline{ \boxed {\sf{mass = 10 \: kg }}}$

➋ We know that:–

$\qquad \bull \bf \: { Potential \: energy=mass \times acceleration \times height}$

$\qquad \quad {:} \longrightarrow\sf \: {potential \: energy = 10 \times 10 \times 10 }$

$\qquad \quad {:} \longrightarrow \underline{ \boxed{\sf \: {potential \: energy = 1000 \: J}}}$

$\large \quad \therefore\sf \: { the \: correct \: option \: is \: \underline{\underline{1000 \: J}}}$

$\large{\underline{\underline{\sf{ \maltese \: {Answer:-}}}}}$

• The potential energy is 1000 J