Secondary 3 Physics Mechanics Quiz

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Secondary 3 Physics Quiz - Mechanics

Name: ____________________
Class: ____________________
Date: ____________________
Score: ________ / 45

Duration: 60 minutes
Total Marks: 45 marks

Instructions:

• Answer all questions.
• Use $g = 10\text{ m s}^{-2}$ where applicable.
• Show all working for calculation questions.
• Express final answers to an appropriate number of significant figures.

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Section A: Multiple Choice (1 mark each)

Circle the correct option.

1. Which of the following is a vector quantity? A) Mass B) Speed C) Displacement D) Time

2. An object is moving with a constant velocity of $5\text{ m s}^{-1}$ to the East. What is its acceleration? A) $0\text{ m s}^{-2}$ B) $5\text{ m s}^{-2}$ to the East C) $5\text{ m s}^{-2}$ to the West D) $10\text{ m s}^{-2}$

3. A ball is thrown vertically upwards. At the maximum height, its: A) Velocity is $10\text{ m s}^{-1}$ and acceleration is $0\text{ m s}^{-2}$ B) Velocity is $0\text{ m s}^{-1}$ and acceleration is $10\text{ m s}^{-2}$ downwards C) Velocity is $0\text{ m s}^{-1}$ and acceleration is $0\text{ m s}^{-2}$ D) Velocity is $10\text{ m s}^{-1}$ and acceleration is $10\text{ m s}^{-2}$ downwards

4. Which of the following describes the property of inertia? A) The ability of an object to accelerate quickly. B) The resistance of an object to change its state of motion. C) The force exerted by gravity on a mass. D) The turning effect of a force.

5. A block of mass $2\text{ kg}$ is pushed across a smooth floor with a net force of $10\text{ N}$. The acceleration is: A) $20\text{ m s}^{-2}$ B) $12\text{ m s}^{-2}$ C) $5\text{ m s}^{-2}$ D) $0.2\text{ m s}^{-2}$

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Section B: Short Answer and Calculations (2-3 marks each)

6. Distinguish between mass and weight. (2)
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7. A car accelerates uniformly from $10\text{ m s}^{-1}$ to $30\text{ m s}^{-1}$ in $4\text{ seconds}$. Calculate the acceleration. (2)
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8. State the Principle of Moments for a body in equilibrium. (2)
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9. A uniform beam of length $4\text{ m}$ is pivoted at its center. A $5\text{ N}$ weight is placed $1\text{ m}$ from the pivot on the left. Where should a $10\text{ N}$ weight be placed on the right to balance the beam? (2)
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10. Define the term "pressure" and state its SI unit. (2)
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11. A cube of side $0.1\text{ m}$ exerts a force of $50\text{ N}$ on a table. Calculate the pressure exerted by the cube. (2)
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12. Explain why a person wearing snowshoes does not sink as deeply into the snow as a person wearing regular boots. (2)
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13. A diver is at a depth of $20\text{ m}$ in a lake (density $= 1000\text{ kg m}^{-3}$). Calculate the pressure exerted by the water on the diver. (2)
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14. State the principle of conservation of energy. (1)
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15. A $0.5\text{ kg}$ ball is held at a height of $2\text{ m}$. Calculate its gravitational potential energy. (2)
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Section C: Structured and Diagram-Based Questions (3-5 marks each)

16. A child of mass $30\text{ kg}$ slides down a vertical rope. If the child's acceleration is $2\text{ m s}^{-2}$ downwards, calculate the frictional force between the child and the rope. (3)
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17. A wooden block of mass $2\text{ kg}$ is pulled up a rough inclined plane at a constant speed by a force of $20\text{ N}$. If the distance moved along the plane is $5\text{ m}$ and the vertical height gained is $3\text{ m}$: (a) Calculate the work done by the pulling force. (2) (b) Calculate the gain in gravitational potential energy. (2) (c) Determine the energy lost to friction. (2)
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18. A ring of mass $0.4\text{ kg}$ is suspended by two strings. String A is at $45^\circ$ to the horizontal and String B is at $60^\circ$ to the horizontal. (a) Draw a free-body diagram of the ring. (2) (b) Describe the condition for the ring to be in equilibrium. (2)
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19. An object of mass $m$ is moving to the right on a smooth surface under a constant force $F_1$. After some time, an opposing force $F_2$ of the same magnitude as $F_1$ is applied. (a) Describe the motion of the object before $F_2$ is applied. (2) (b) Describe the motion of the object after $F_2$ is applied. (2)
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20. A ball is released from rest and falls through the air. (a) Describe the motion of the ball immediately after release, ignoring air resistance. (2) (b) Explain how the motion changes as the ball reaches terminal velocity, considering the effect of air resistance. (3)
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Answers: Secondary 3 Physics Quiz - Mechanics

1. C (Displacement)

2. A ($0\text{ m s}^{-2}$ - constant velocity means no acceleration)

3. B (Velocity is 0 at peak; acceleration is always $g$ downwards)

4. B (Resistance to change in motion)

5. C ($a = F/m = 10/2 = 5\text{ m s}^{-2}$)

6. Mass is the amount of matter in an object (kg, scalar). Weight is the gravitational force acting on an object (N, vector). (2)

7. $a = \frac{v - u}{t} = \frac{30 - 10}{4} = \frac{20}{4} = 5\text{ m s}^{-2}$ (2)

8. For a body in equilibrium, the sum of clockwise moments about a pivot is equal to the sum of anticlockwise moments about the same pivot. (2)

9. Anticlockwise moment = $5\text{ N} \times 1\text{ m} = 5\text{ Nm}$. Clockwise moment = $10\text{ N} \times d$. $10d = 5 \implies d = 0.5\text{ m}$ from the pivot. (2)

10. Pressure is the force exerted per unit area. SI unit: Pascal (Pa) or $\text{N m}^{-2}$. (2)

11. Area $= 0.1 \times 0.1 = 0.01\text{ m}^2$. $P = F/A = 50 / 0.01 = 5000\text{ Pa}$. (2)

12. Snowshoes have a larger surface area. For the same weight (force), a larger area results in lower pressure exerted on the snow, preventing the person from sinking. (2)

13. $P = h\rho g = 20 \times 1000 \times 10 = 200,000\text{ Pa}$ (or $2 \times 10^5\text{ Pa}$). (2)

14. Energy cannot be created or destroyed, only transformed from one form to another. (1)

15. $GPE = mgh = 0.5 \times 10 \times 2 = 10\text{ J}$. (2)

16. $F_{\text{net}} = ma$ $mg - f = ma$ $(30 \times 10) - f = 30 \times 2$ $300 - f = 60 \implies f = 240\text{ N}$. (3)

17. (a) $W = F \times d = 20 \times 5 = 100\text{ J}$. (2) (b) $\Delta GPE = mgh = 2 \times 10 \times 3 = 60\text{ J}$. (2) (c) Energy loss $= W_{\text{applied}} - \Delta GPE = 100 - 60 = 40\text{ J}$. (2)

18. (a) Diagram should show: Weight ($W$) acting downwards, Tension $T_A$ at $45^\circ$ (up-left), Tension $T_B$ at $60^\circ$ (up-right). (2) (b) The resultant force must be zero. The sum of vertical components of tensions must equal the weight, and the sum of horizontal components must be zero. (2)

19. (a) The object accelerates uniformly to the right because there is a net unbalanced force $F_1$. (2) (b) The net force becomes zero ($F_1 - F_2 = 0$). The object continues to move to the right at a constant velocity (zero acceleration). (2)

20. (a) The ball accelerates downwards at $10\text{ m s}^{-2}$ (free fall). (2) (b) As speed increases, air resistance (drag) increases. The net force ($W - \text{drag}$) decreases, causing acceleration to decrease. When drag equals weight, net force is zero and the ball moves at a constant terminal velocity. (3)