QUARTER FINAL STAGE 2024
Accra Academy: 45 points
Oyoko Methodist SHS: 36 points
St. Joseph Seminary SHS: 28 points
ROUND 4 - TRUE OR FALSE
SECOND SET OF QUESTIONS
PREAMBLE
An object moves with constant speed.
1. The object moves with zero acceleration.
ANSWER: FALSE
EXPLANATION:
Acceleration is the rate of change of velocity.
Velocity is a vector quantity having both speed and direction.
If an object moves in a curved or circular path, its direction changes continuously.
This change in direction creates a non-zero centripetal acceleration, even if its speed remains constant.
Therefore, a constant speed does not always guarantee zero acceleration.
2. The object moves with constant acceleration.
ANSWER: FALSE
EXPLANATION:
An object moving with constant speed can experience a changing acceleration vector.
For example, in uniform circular motion, the magnitude of the acceleration remains constant, but its direction constantly shifts toward the center of the path.
Since acceleration is a vector quantity, a change in its direction means the acceleration itself is not constant.
3. The object moves with constant velocity.
ANSWER: FALSE
EXPLANATION:
Velocity requires both speed and direction to remain unchanged.
If an object turns, changes lanes, or travels along a curved track, its direction changes.
As a result, its velocity is changing even though its speed stays constant.
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PRACTICE QUESTIONS
PREAMBLE 1
An object moves with a constant velocity.
1. The object moves along a straight path.
ANSWER: TRUE
EXPLANATION:
Constant velocity means that the direction of motion cannot change.
An object that never changes its direction must travel in a single straight line.
2. The object can move in a uniform circle.
ANSWER: FALSE
EXPLANATION:
Moving in a circle requires the direction of motion to change continuously.
Any change in direction alters the velocity vector, making it impossible for the velocity to remain constant.
3. The object's kinetic energy remains constant.
ANSWER: TRUE
EXPLANATION:
KE $=\dfrac{1}{2}mv^2$.
Since the speed $v$ is constant, KE is constant.
PREAMBLE 2
An object moves with a constant velocity.
1. The object's acceleration vector changes direction over time.
ANSWER: FALSE
EXPLANATION:
The acceleration is exactly zero at every instant.
A zero vector has no direction, so there is no direction to change.
2. The net force on the object is zero.
ANSWER: TRUE
EXPLANATION:
By Newton's second law, $F_{net}=ma$.
Zero acceleration means zero net force.
3. The object's displacement is directly proportional to time elapsed.
ANSWER: TRUE
EXPLANATION:
For constant velocity, $s=vt$.
Displacement is therefore directly proportional to time.
PREAMBLE 3
An object moves with a constant velocity.
1. The object can be undergoing projectile motion.
ANSWER: FALSE
EXPLANATION:
Projectile motion always has a non-zero vertical acceleration due to gravity.
The velocity of a projectile therefore cannot stay constant.
2. The object's velocity-time graph is a horizontal line.
ANSWER: TRUE
EXPLANATION:
A constant velocity never changes with time.
Its graph against time is therefore a horizontal line.
3. The object's position-time graph is a straight line (assuming $v\ne0$).
ANSWER: TRUE
EXPLANATION:
$s=vt$ is linear in $t$.
This gives a straight-line graph with a non-zero slope.
PREAMBLE 4
An object moves with a constant velocity.
1. The momentum of the object is changing.
ANSWER: FALSE
EXPLANATION:
$p=mv$.
With constant mass and constant $v$, the momentum is constant.
2. The object could be permanently at rest.
ANSWER: TRUE
EXPLANATION:
Zero is itself a constant value.
A stationary object therefore satisfies "constant velocity."
3. The distance travelled equals the magnitude of the displacement over any time interval.
ANSWER: TRUE
EXPLANATION:
Constant velocity means straight-line motion in one direction.
Distance therefore equals $|\text{displacement}|$ exactly.