Gravitational PE (Near Earth) — Practice Quiz

Question 1

Gravitational PE of 1 kg at Earth's surface (M = 6×10²⁴ kg, R = 6.4×10⁶ m):

Accepted Answer

−6.25 × 10⁷ J

Answer

0

Answer

+6.25 × 10⁷ J

Answer

−9.8 J

Question 2

An object falls from height h above Earth's surface. Loss in PE (h ≪ R):

Accepted Answer

mgh

Answer

−mgh

Answer

GMm/h

Answer

mgh/2

Question 3

Total energy of a body in circular orbit at radius r:

Accepted Answer

−GMm/(2r)

Answer

+GMm/r

Answer

−GMm/r

Answer

+GMm/(2r)

Question 4

Work done by gravity from r₁ to r₂ (r₂ > r₁):

Accepted Answer

−GMm·(1/r₁ − 1/r₂)

Answer

+GMm·(1/r₁ − 1/r₂)

Answer

Zero

Answer

Always positive

Question 5

Gravitational PE near Earth's surface (mgh) is an approximation valid when:

Accepted Answer

h ≪ R (Earth's radius)

Answer

h is very large

Answer

h = R

Answer

Always