QUARTER FINAL STAGE 2024
Accra Academy: 45 points
Oyoko Methodist SHS: 36 points
St. Joseph Seminary SHS: 28 points
ROUND 2 - SPEED RACE
QUESTION
Find the kinetic energy of a 25kg object moving at $12\text{ m/s}$.
ANSWER: 1800 J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 25 \times 12^2$
$KE = \dfrac{1}{2} \times 25 \times 144$
$KE = 25 \times 72$
$KE = 1800\text{ J}$
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PRACTICE QUESTIONS
1. QUESTION: Find the kinetic energy of a 2.0 kg object moving at 3.0 m/s.
ANSWER: 9.0 J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 2.0 \times (3.0)^2$
$KE = \dfrac{1}{2} \times 2.0 \times 9.0$
$KE = 9.0\text{ J}$
2. QUESTION: Find the kinetic energy of a 4.0 kg object moving at 6.0 m/s.
ANSWER: 72 J or $7.2\times10^{1}$ J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 4.0 \times (6.0)^2$
$KE = \dfrac{1}{2} \times 4.0 \times 36$
$KE = 2 \times 36$
$KE = 72\text{ J}$
3. QUESTION: Find the kinetic energy of a 6.0 kg object moving at 4.0 m/s.
ANSWER: 48 J or $4.8\times10^{1}$ J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 6.0 \times (4.0)^2$
$KE = \dfrac{1}{2} \times 6.0 \times 16$
$KE = 3 \times 16$
$KE = 48\text{ J}$
4. QUESTION: Find the kinetic energy of a 3.0 kg object moving at 6.0 m/s.
ANSWER: 54 J or $5.4\times10^{1}$ J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 3.0 \times (6.0)^2$
$KE = \dfrac{1}{2} \times 3.0 \times 36$
$KE = 3 \times 18$
$KE = 54\text{ J}$
5. QUESTION: Find the kinetic energy of a 1.5 kg object moving at 4.0 m/s.
ANSWER: 12 J or $1.2\times10^{1}$ J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 1.5 \times (4.0)^2$
$KE = \dfrac{1}{2} \times 1.5 \times 16$
$KE = \dfrac{15\times10^{-1} \times 16}{2}$
$KE = 15 \times 8 \times10^{-1}$
$KE = 12\text{ J}$
6. QUESTION: Find the kinetic energy of a 0.60 kg object moving at 5.0 m/s.
ANSWER: 7.5 J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 0.60 \times (5.0)^2$
$KE = \dfrac{1}{2} \times 0.60 \times 25$
$KE = \dfrac{6\times10^{-1} \times 25}{2}$
$KE = 3 \times 25 \times10^{-1}$
$KE = 7.5\text{ J}$
7. QUESTION: Find the kinetic energy of a 5.0 kg object moving at 8.0 m/s.
ANSWER: 160 J or $1.6\times10^{2}$ J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 5.0 \times (8.0)^2$
$KE = \dfrac{1}{2} \times 5.0 \times 64$
$KE = 5 \times 32$
$KE = 1.6\times10^{2}\text{ J}$
8. QUESTION: Find the kinetic energy of a 12 kg object moving at 5.0 m/s.
ANSWER: 150 J or $1.5\times10^{2}$ J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 12 \times (5.0)^2$
$KE = \dfrac{1}{2} \times 12 \times 25$
$KE = 6 \times 25$
$KE = 1.5\times10^{2}\text{ J}$
9. QUESTION: Find the kinetic energy of a 0.50 kg object moving at 1.0 m/s.
ANSWER: 0.25 J or $2.5\times10^{-1}$ J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 0.50 \times (1.0)^2$
$KE = \dfrac{1}{2} \times 0.50 \times 1.0$
$KE = \dfrac{5\times10^{-1}}{2}$
$KE = 0.25\text{ J}$
10. QUESTION: Find the kinetic energy of a 0.80 kg object moving at 3.0 m/s.
ANSWER: 3.6 J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 0.80 \times (3.0)^2$
$KE = \dfrac{1}{2} \times 0.80 \times 9.0$
$KE = \dfrac{8\times10^{-1} \times 9}{2}$
$KE = 4 \times 9 \times10^{-1}$
$KE \approx 3.6\text{ J}$
11. QUESTION: Find the kinetic energy of a 7.0 kg object moving at 6.0 m/s.
ANSWER: 130 J or $1.3\times10^{2}$ J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 7.0 \times (6.0)^2$
$KE = \dfrac{1}{2} \times 7.0 \times 36$
$KE = 7 \times 18$
$KE \approx 1.3\times10^{2}\text{ J}$
12. QUESTION: Find the kinetic energy of a 9.0 kg object moving at 2.0 m/s.
ANSWER: 18 J or $1.8\times10^{1}$ J
SOLUTION:
$KE = \dfrac{1}{2}mv^2$
$KE = \dfrac{1}{2} \times 9.0 \times (2.0)^2$
$KE = \dfrac{1}{2} \times 9.0 \times 4.0$
$KE = 9 \times 2$
$KE = 18\text{ J}$