PRELIMINARY STAGE 2024
Contest 34
T.I. AMASS, Kumasi: 71 points (Winner)
Amenfiman SHS: 40 points
Tuobodom SHTS: 21 points
Contest 35
Accra Girls’ SHS: 39 points (Winner)
Notre Dame Girls’ SHS: 34 points
Aburi Girls’ SHS: 27 points
Contest 36
Anlo SHS: 69 points (Winner)
Tamale Islamic Science SHS: 34 points
Yendi SHS: 28 points
ROUND 4 - TRUE OR FALSE
ROUND 4 TRUE OR FALSE
PREAMBLE
As a car rounds a curve on a road, a backseat passenger slides towards one side of the car.
1. The force pushing the passenger to one side of the car is friction.
ANSWER: FALSE
EXPLANATION:
Friction resists motion, it does not push the passenger sideways.
2. The force pushing the passenger to one side of the car is centripetal force.
ANSWER: FALSE
EXPLANATION:
Centripetal force acts towards the center of the curve, not sideways relative to the car.
3. There is no force pushing the passenger to one side of the car.
ANSWER: TRUE
EXPLANATION:
The sliding sensation is due to the passenger’s inertia (tendency to move straight), not any lateral force.
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PRACTICE QUESTIONS
PREAMBLE 1
A car travels at constant speed around a flat circular bend.
1. Friction between the tyres and the road provides the centripetal force.
ANSWER: TRUE
EXPLANATION:
On a flat road, sideways friction is the only horizontal force towards the centre.
2. The car is accelerating.
ANSWER: TRUE
EXPLANATION:
Its direction of motion keeps changing.
3. The resultant force on the car points away from the centre of the bend.
ANSWER: FALSE
EXPLANATION:
It points towards the centre.
PREAMBLE 2
A bucket of water is whirled in a vertical circle fast enough that the water stays in at the top.
1. At the top, the weight of the water helps to provide the centripetal force.
ANSWER: TRUE
EXPLANATION:
Weight acts towards the centre at the top.
2. An outward centrifugal force holds the water in the bucket.
ANSWER: FALSE
EXPLANATION:
In the ground frame only weight and the push of the bucket act, both towards the centre.
3. At the top, the bucket must still push down on the water.
ANSWER: FALSE
EXPLANATION:
At the minimum speed the weight alone provides the centripetal force.
PREAMBLE 3
A stone tied to a string is whirled in a horizontal circle and the string breaks.
1. The stone flies off along the tangent to the circle.
ANSWER: TRUE
EXPLANATION:
No centripetal force acts, so it moves in a straight line.
2. The stone flies off along the radius, away from the centre.
ANSWER: FALSE
EXPLANATION:
It continues in the direction it was moving, which is tangential.
3. The tension in the string was the centripetal force.
ANSWER: TRUE
EXPLANATION:
The string pulled the stone towards the centre.