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O Level Physics Mechanics Quiz

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Questions

O-Level Physics Quiz - Mechanics

Name: __________________________
Class: __________________________
Date: __________________________
Score: _________ / 40

Duration: 45 minutes
Total Marks: 40

Instructions:

Answer all questions.
Write your answers in the spaces provided.
Show all working clearly. Marks are awarded for correct methods even if the final answer is incorrect.
Use $g = 10 \text{ m/s}^2$ for calculations involving gravity unless stated otherwise.

Section A: Multiple Choice & Short Concepts (10 Marks)

1. A car travels along a straight road. It travels 100 m North in 10 s, then immediately travels 50 m South in 5 s. What is the average velocity of the car for the entire journey?
[1]

A. 3.3 m/s North
B. 10 m/s North
C. 3.3 m/s South
D. 10 m/s South

Answer: __________________________

2. Which of the following quantities is a vector?
[1]

A. Mass
B. Speed
C. Distance
D. Acceleration

Answer: __________________________

3. A book rests on a horizontal table. Which pair of forces acts on the book to keep it in equilibrium?
[1]

A. The weight of the book and the normal contact force from the table.
B. The weight of the book and the gravitational pull of the book on the Earth.
C. The normal contact force from the table and the force of the book on the table.
D. The friction force and the applied push.

Answer: __________________________

4. State the SI unit for pressure.
[1]

Answer: __________________________

5. Define the term inertia.
[1]

Answer:

6. A hydraulic press is used to lift a heavy load. Explain why liquids are used in hydraulic systems instead of gases.
[1]

Answer:

7. The diagram below shows a uniform metre rule pivoted at the 50 cm mark. A 2 N weight is hung at the 20 cm mark. Where must a 3 N weight be hung to balance the rule?
[1]

A. 30 cm mark
B. 60 cm mark
C. 70 cm mark
D. 80 cm mark

Answer: __________________________

8. Which energy store increases when a spring is compressed?
[1]

A. Kinetic energy
B. Gravitational potential energy
C. Elastic potential energy
D. Chemical energy

Answer: __________________________

9. A student climbs a flight of stairs. Which quantity is NOT needed to calculate the useful power developed by the student?
[1]

A. The mass of the student
B. The vertical height of the stairs
C. The time taken to climb the stairs
D. The length of the stairs along the slope

Answer: __________________________

10. An object is moving at a constant speed in a circular path. Which statement is correct?
[1]

A. The velocity is constant.
B. The acceleration is zero.
C. There is a resultant force acting on the object.
D. The kinetic energy is changing.

Answer: __________________________

Section B: Structured Questions (20 Marks)

11. The velocity-time graph below shows the motion of a train travelling between two stations.

(Imagine a graph: Velocity increases linearly from 0 to 20 m/s in 10 s, stays constant at 20 m/s for 30 s, then decreases linearly to 0 in 10 s.)

(a) Calculate the acceleration of the train during the first 10 seconds.
[2]

Working:
 Answer: __________________________ m/s²

(b) Calculate the total distance travelled by the train.
[3]

Working:
 Answer: __________________________ m

Answer:

12. A box of mass 50 kg is pushed across a horizontal floor. The pushing force is 200 N, and the frictional force opposing the motion is 80 N.

(a) Calculate the resultant force acting on the box.
[1]

Working:
 Answer: __________________________ N

(b) Calculate the acceleration of the box.
[2]

Working:
 Answer: __________________________ m/s²

(c) The pushing force is removed. The box continues to slide for a short distance before stopping. Explain why the box does not stop immediately.
[2]

Answer:

13. A diver is swimming at a depth of 15 m below the surface of the sea. The density of sea water is 1030 kg/m³. Atmospheric pressure is 100,000 Pa.

(a) Calculate the pressure due to the column of sea water at this depth.
[2]

Working:
 Answer: __________________________ Pa

(b) Calculate the total pressure acting on the diver.
[1]

Working:
 Answer: __________________________ Pa

Answer:

14. A uniform beam of length 4.0 m and weight 200 N is pivoted at one end. A load of 300 N is suspended from the other end. A vertical cable supports the beam at its midpoint (2.0 m from the pivot).

(a) State the Principle of Moments.
[1]

Answer:

(b) Calculate the tension in the cable required to keep the beam horizontal.
[3]

Working:
 Answer: __________________________ N

Section C: Free Response & Application (10 Marks)

15. A crane lifts a container of mass 2000 kg vertically upwards at a constant speed of 0.5 m/s.

(a) Calculate the weight of the container.
[1]

Working:
 Answer: __________________________ N

(b) State the magnitude of the upward force exerted by the crane on the container. Explain your answer.
[2]

Answer:
Force: __________________________ N
Explanation:

Working:
 Answer: __________________________ W

(d) The crane engine consumes fuel to provide this energy. Explain why the efficiency of the crane is less than 100%.
[2]

Answer:

16. A student investigates the relationship between the extension of a spring and the load applied.

(a) Sketch a graph of Extension (y-axis) against Load (x-axis) for a spring that obeys Hooke’s Law up to its limit of proportionality. Label the limit of proportionality.
[2]

Space for Graph:

(b) Beyond the limit of proportionality, the spring is permanently deformed. What is this type of deformation called?
[1]

Answer: __________________________ deformation

17. A cyclist travels at a constant speed of 5 m/s. The total resistive force acting on the cyclist and bicycle is 40 N.

(a) State the magnitude of the forward force applied by the cyclist.
[1]

Answer: __________________________ N

(b) Calculate the power developed by the cyclist.
[2]

Working:
 Answer: __________________________ W

18. A metal block has a mass of 500 g and a volume of 100 cm³.

(a) Calculate the density of the metal block in g/cm³.
[1]

Working:
 Answer: __________________________ g/cm³

(b) Convert this density into kg/m³.
[1]

Working:
 Answer: __________________________ kg/m³

19. A ball is dropped from a height. Air resistance is negligible.

(a) Describe the energy transformation that occurs as the ball falls.
[1]

Answer:

(b) If the ball hits the ground and does not bounce back to its original height, explain where the "missing" energy has gone.
[1]

Answer:

20. A force of 10 N is applied to an object, causing it to move 5 m in the direction of the force.

(a) Calculate the work done by the force.
[1]

Working:
 Answer: __________________________ J

(b) If this work is done in 2 seconds, calculate the power.
[1]

Working:
 Answer: __________________________ W

Answers

O-Level Physics Quiz - Mechanics (Answer Key)

1. A
Reasoning: Total displacement = $100 \text{ m (N)} - 50 \text{ m (S)} = 50 \text{ m North}$ . Total time = $10 + 5 = 15 \text{ s}$ . Average velocity = $50 / 15 = 3.33 \text{ m/s North}$ .

2. D
Reasoning: Acceleration has both magnitude and direction. Mass, speed, and distance are scalars.

3. A
Reasoning: For equilibrium, forces must act on the same object and be equal and opposite. Weight (down) and Normal Contact Force (up) act on the book.

4. Pascal (Pa) or N/m²

5. Inertia is the resistance of an object to change its state of motion (or rest).

6. Liquids are incompressible (or virtually incompressible), allowing pressure to be transmitted equally and instantly throughout the fluid without loss of volume. Gases are compressible.

7. C
Reasoning: Moment clockwise = Moment anticlockwise.
Anticlockwise Moment: $2 \text{ N} \times (50 - 20) \text{ cm} = 2 \times 30 = 60 \text{ N cm}$ .
Clockwise Moment: $3 \text{ N} \times d = 60 \text{ N cm} \Rightarrow d = 20 \text{ cm}$ .
Position = $50 \text{ cm} + 20 \text{ cm} = 70 \text{ cm}$ mark.

8. C
Reasoning: Compressing a spring stores energy as elastic potential energy.

9. D
Reasoning: Power = Work / Time. Work against gravity = $mgh$ . Length of slope is irrelevant for useful power against gravity.

10. C
Reasoning: Velocity changes direction, so there is acceleration. Acceleration requires a resultant force (centripetal force). Speed is constant, so KE is constant.

11. (a) Acceleration = Gradient of v-t graph.
$a = \frac{\Delta v}{\Delta t} = \frac{20 - 0}{10} = \mathbf{2.0 \text{ m/s}^2}$

(b) Distance = Area under v-t graph.
Area = Area of triangle 1 + Area of rectangle + Area of triangle 2
$= (\frac{1}{2} \times 10 \times 20) + (30 \times 20) + (\frac{1}{2} \times 10 \times 20)$
$= 100 + 600 + 100 = \mathbf{800 \text{ m}}$

(c) The driving force is equal in magnitude and opposite in direction to the resistive forces (friction/air resistance). Therefore, the resultant force is zero, so there is no acceleration (Newton's First Law).

12. (a) Resultant Force = Push - Friction = $200 - 80 = \mathbf{120 \text{ N}}$

(b) $F = ma \Rightarrow 120 = 50 \times a$
$a = \frac{120}{50} = \mathbf{2.4 \text{ m/s}^2}$

(c) The box has inertia (or momentum). It resists the change in its state of motion. Friction acts to decelerate it, but it takes time/distance to bring the velocity to zero.

13. (a) Pressure due to liquid column $P = h \rho g$
$P = 15 \times 1030 \times 10 = \mathbf{154,500 \text{ Pa}}$

(b) Total Pressure = Atmospheric Pressure + Liquid Pressure
$P_{total} = 100,000 + 154,500 = \mathbf{254,500 \text{ Pa}}$

(c) The pressure increases.
Explanation: Pressure is directly proportional to depth ( $P = h \rho g$ ). As depth doubles, the pressure due to the water column doubles, increasing the total pressure.

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

(b) Pivot at one end (0 m).
Clockwise Moments:

Weight of beam acts at centre (2.0 m): $200 \text{ N} \times 2.0 \text{ m} = 400 \text{ Nm}$
Load acts at end (4.0 m): $300 \text{ N} \times 4.0 \text{ m} = 1200 \text{ Nm}$
Total Clockwise Moment = $1600 \text{ Nm}$

Anticlockwise Moment:
Tension $T$ acts at midpoint (2.0 m): $T \times 2.0 \text{ m}$

Equilibrium: $2.0 T = 1600$
$T = \frac{1600}{2.0} = \mathbf{800 \text{ N}}$

15. (a) Weight $W = mg = 2000 \times 10 = \mathbf{20,000 \text{ N}}$

(b) Force = 20,000 N
Explanation: Since the container moves at a constant speed, the acceleration is zero. Therefore, the resultant force is zero. The upward force must balance the downward weight.

(c) Power $P = F \times v$ (or Work/time)
$P = 20,000 \text{ N} \times 0.5 \text{ m/s} = \mathbf{10,000 \text{ W}}$ (or 10 kW)

(d) Energy is wasted/lost as heat (due to friction in moving parts) and sound. Also, some energy is used to lift the crane's own hook/cables. Thus, useful output energy < total input energy.

16. (a) Graph should show a straight line passing through the origin. The line should curve or stop at the "Limit of Proportionality".
Labels: y-axis "Extension", x-axis "Load". Point marked "Limit of Proportionality".

(b) Plastic (or Inelastic) deformation.

17. (a) 40 N
Reasoning: At constant speed, acceleration is zero, so resultant force is zero. Forward force equals resistive force.

(b) Power $P = F \times v$
$P = 40 \text{ N} \times 5 \text{ m/s} = \mathbf{200 \text{ W}}$

18. (a) Density $\rho = \frac{m}{V}$
$\rho = \frac{500}{100} = \mathbf{5 \text{ g/cm}^3}$

(b) To convert g/cm³ to kg/m³, multiply by 1000.
$5 \times 1000 = \mathbf{5000 \text{ kg/m}^3}$

19. (a) Gravitational potential energy is converted into kinetic energy.

(b) The energy is converted into heat (thermal energy) and sound upon impact with the ground (and deformation of the ball/ground).

20. (a) Work Done $W = F \times d$
$W = 10 \text{ N} \times 5 \text{ m} = \mathbf{50 \text{ J}}$

(b) Power $P = \frac{W}{t}$
$P = \frac{50 \text{ J}}{2 \text{ s}} = \mathbf{25 \text{ W}}$