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When a ball thrown upwards reaches its highest point, tick which of the following statement(s) are correct?
(i) The force acting on the ball is zero.
(ii) The acceleration of the ball is zero.
(iii) Its kinetic energy is zero.
(iv) Its potential energy is maximum.
Show Answer
Correct: (iii) and (iv) .
At the highest point the ball is momentarily at rest, so its kinetic energy is zero (iii) and its potential energy is maximum (iv). The force of gravity still acts, so the force is not zero and the acceleration is g (not zero) — (i) and (ii) are wrong.
At the highest point — what is TRUE
What is FALSE
(iii) Kinetic energy is zero
— the ball has stopped rising, v = 0
(i) The force is zero —
no
, gravity still acts (mg)
(iv) Potential energy is maximum
— it is at its greatest height
(ii) The acceleration is zero —
no
, a = g, still 10 m s⁻² downwards
All the KE has turned into PE
Zero velocity does
not
mean zero force or zero acceleration
⇒ correct options are
(iii)
and
(iv)
—
