Energy Conservation in Projectile Motion

Steps:

• Ball starts with initial kinetic energy (KE_i) and zero gravitational potential energy (PE=0).
• Total mechanical energy E = KE + PE remains constant as it rises, with KE converting to PE = mgh.
• Maximum height h_max occurs when KE=0, so PE_max = KE_i = mgh_max.
• Midpoint height is h_max/2, so PE = mg(h_max/2) = (1/2)KE_i, not equal to KE_i.

Why B is correct:

• At midpoint, PE = (1/2) initial KE by energy conservation, but B claims PE equals initial KE, violating the formula PE = mgh.

Why the others are wrong:

• A: Correct; KE decreases as PE increases during ascent.
• C: Correct; velocity is zero at top, so KE=0.
• D: Incorrect; total energy is conserved and equals initial total energy.

Final answer: B