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Secondary 3 Physics Mechanics Quiz

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Secondary 3 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.
Take the acceleration due to gravity, $g = 10 \text{ m/s}^2$ .
Show all working clearly. Marks are awarded for correct reasoning and steps, not just the final answer.

Section A: Kinematics and Measurements (Questions 1–5)

1. A student measures the diameter of a steel ball using a micrometer screw gauge. The main scale reading is 5.5 mm and the thimble scale reading is 0.28 mm. (a) State the total reading of the micrometer.

_________________________________________________________________________ [1]

(b) Explain why a micrometer is more suitable than a metre rule for this measurement.

_________________________________________________________________________ [1]

2. The displacement-time graph below shows the motion of a cyclist.

(Imagine a graph: From t=0 to t=10s, displacement increases linearly from 0m to 50m. From t=10s to t=20s, displacement remains constant at 50m. From t=20s to t=30s, displacement decreases linearly from 50m to 0m.)

(a) Calculate the velocity of the cyclist during the first 10 seconds.

_________________________________________________________________________ [2]

(b) Describe the motion of the cyclist between t = 10 s and t = 20 s.

_________________________________________________________________________ [1]

3. A car accelerates uniformly from rest to a velocity of 20 m/s in 5 seconds. It then travels at this constant velocity for 10 seconds before decelerating uniformly to rest in 4 seconds. (a) Sketch the velocity-time graph for this motion on the axes below. Label the values on the axes.

Velocity (m/s)
   |
   |
   |
   |
   |
   |________________________________________ Time (s)

[2]

(b) Calculate the total distance traveled by the car.

_________________________________________________________________________ [2]

4. Which of the following pairs contains one scalar quantity and one vector quantity? A. Mass and Weight
B. Speed and Velocity
C. Distance and Displacement
D. All of the above

Answer: __________ [1]

5. A stone is dropped from the top of a cliff. Air resistance is negligible. (a) State the value of the acceleration of the stone just after it is released.

_________________________________________________________________________ [1]

(b) Explain why the acceleration remains constant as the stone falls.

_________________________________________________________________________ [1]

Section B: Dynamics and Forces (Questions 6–10)

6. A block of mass 5 kg rests on a horizontal rough surface. A horizontal force of 20 N is applied to the block, but it does not move. (a) State the magnitude of the frictional force acting on the block.

_________________________________________________________________________ [1]

(b) Explain why the block does not move in terms of forces.

_________________________________________________________________________ [1]

7. A skydiver of mass 80 kg jumps from a plane. (a) Calculate the weight of the skydiver.

_________________________________________________________________________ [1]

(b) As the skydiver falls, air resistance increases. Describe and explain what happens to the skydiver’s acceleration.

_________________________________________________________________________ [2]

8. Two forces act on an object: 3 N due North and 4 N due East. (a) Draw a vector diagram to show how to find the resultant force.

[1]

(b) Calculate the magnitude of the resultant force.

_________________________________________________________________________ [1]

9. A car of mass 1000 kg is traveling at 15 m/s. The driver applies the brakes, and a constant braking force of 5000 N acts on the car. (a) Calculate the deceleration of the car.

_________________________________________________________________________ [2]

(b) Calculate the time taken for the car to come to a stop.

_________________________________________________________________________ [2]

10. Newton’s Third Law states that for every action, there is an equal and opposite reaction. A book rests on a table. The weight of the book acts downwards. (a) Identify the "reaction" force to the weight of the book.

_________________________________________________________________________ [1]

(b) Identify the "reaction" force to the normal contact force of the table pushing up on the book.  

_________________________________________________________________________ [1]

Section C: Turning Effects, Pressure, and Energy (Questions 11–15)

11. A uniform metre rule is pivoted at the 50 cm mark. A 2 N weight is hung at the 10 cm mark. (a) Calculate the moment of the 2 N weight about the pivot.

_________________________________________________________________________  
_________________________________________________________________________ [2]

(b) Where must a 4 N weight be placed on the right side of the pivot to balance the rule?  

_________________________________________________________________________  
_________________________________________________________________________ [2]

12. Explain why a sharp knife cuts better than a blunt knife, referring to the concept of pressure.

_________________________________________________________________________  
_________________________________________________________________________  
_________________________________________________________________________ [2]

13. A diver is swimming at a depth of 10 m in sea water. The density of sea water is 1030 kg/m³. (a) Calculate the pressure due to the water column at this depth. ( $g = 10 \text{ N/kg}$ )

_________________________________________________________________________  
_________________________________________________________________________ [2]

(b) The atmospheric pressure is 100,000 Pa. Calculate the total pressure acting on the diver.  

_________________________________________________________________________ [1]

14. A crane lifts a load of 500 kg vertically through a height of 20 m in 10 seconds. (a) Calculate the work done by the crane against gravity.

_________________________________________________________________________  
_________________________________________________________________________ [2]

(b) Calculate the power developed by the crane.  

_________________________________________________________________________  
_________________________________________________________________________ [2]

15. A ball of mass 0.5 kg is thrown vertically upwards with an initial speed of 10 m/s. Air resistance is negligible. (a) Calculate the initial kinetic energy of the ball.

_________________________________________________________________________  
_________________________________________________________________________ [2]

(b) Calculate the maximum height reached by the ball.  

_________________________________________________________________________  
_________________________________________________________________________ [2]

Section D: Synthesis and Application (Questions 16–20)

16. A trolley runs down a friction-compensated runway. (a) What does "friction-compensated" mean?

_________________________________________________________________________  
_________________________________________________________________________ [1]

(b) If the runway is tilted further, describe the motion of the trolley.  

_________________________________________________________________________ [1]

17. A hydraulic press consists of two pistons, A and B. Piston A has an area of 0.01 m² and Piston B has an area of 0.1 m². A force of 100 N is applied to Piston A. (a) Calculate the pressure transmitted through the liquid.

_________________________________________________________________________  
_________________________________________________________________________ [2]

(b) Calculate the output force on Piston B.  

_________________________________________________________________________  
_________________________________________________________________________ [2]

18. A student investigates the relationship between force and acceleration using a trolley and ticker-tape timer. (a) State the variable that must be kept constant to ensure a fair test.

_________________________________________________________________________ [1]

(b) Sketch the expected graph of Acceleration (y-axis) against Force (x-axis).  

```
Accel
  |
  |
  |
  |
  |____________________ Force
```
[1]

19. A box slides down a rough inclined plane at a constant speed. (a) Is the net force on the box zero, upwards, or downwards along the plane?

_________________________________________________________________________ [1]

(b) Describe the energy changes taking place as the box slides down.  

_________________________________________________________________________  
_________________________________________________________________________ [2]

20. A satellite orbits the Earth at a constant speed. (a) Is the satellite accelerating? Explain your answer.

_________________________________________________________________________  
_________________________________________________________________________ [2]

(b) Name the force that provides the centripetal acceleration for the satellite.  

_________________________________________________________________________ [1]

End of Quiz

Answers

Secondary 3 Physics Quiz - Mechanics (Answer Key)

1. (a) $5.5 \text{ mm} + 0.28 \text{ mm} = 5.78 \text{ mm}$ [1] (b) Micrometer has a smaller precision/resolution (0.01 mm) compared to a metre rule (1 mm), allowing for more accurate measurement of small diameters. [1]

2. (a) Velocity = Gradient = $\frac{\Delta s}{\Delta t} = \frac{50 - 0}{10 - 0} = 5 \text{ m/s}$ . [2] (b) The cyclist is stationary (at rest) because the displacement does not change with time. [1]

3. (a) Graph should show:

Straight line from (0,0) to (5,20).
Horizontal line from (5,20) to (15,20).
Straight line from (15,20) to (19,0).
Axes labeled with units. [2] (b) Distance = Area under graph. Area 1 (Triangle) = $0.5 \times 5 \times 20 = 50 \text{ m}$ Area 2 (Rectangle) = $10 \times 20 = 200 \text{ m}$ Area 3 (Triangle) = $0.5 \times 4 \times 20 = 40 \text{ m}$ Total Distance = $50 + 200 + 40 = 290 \text{ m}$ . [2]

4. D [1] (Note: Mass/Weight, Speed/Velocity, Distance/Displacement are all Scalar/Vector pairs respectively.)

5. (a) $10 \text{ m/s}^2$ [1] (b) The only force acting is gravity (weight), which is constant near the Earth's surface. Since $F=ma$ and $F$ (weight) is constant, $a$ is constant. [1]

6. (a) 20 N [1] (b) The applied force is balanced by the static frictional force. The resultant force is zero, so there is no acceleration/motion. [1]

7. (a) $W = mg = 80 \times 10 = 800 \text{ N}$ . [1] (b) Acceleration decreases. As speed increases, air resistance increases. The resultant force ( $Weight - Air Resistance$ ) decreases. Since $F=ma$ , acceleration decreases. [2]

8. (a) Diagram showing two perpendicular vectors (3 units and 4 units) forming two sides of a triangle or rectangle, with the resultant as the diagonal. [1] (b) $R = \sqrt{3^2 + 4^2} = \sqrt{9+16} = \sqrt{25} = 5 \text{ N}$ . [1] (c) $\tan(\theta) = \frac{4}{3} \Rightarrow \theta = 53.1^\circ$ East of North (or bearing 053.1°). [1]

9. (a) $F = ma \Rightarrow -5000 = 1000 \times a \Rightarrow a = -5 \text{ m/s}^2$ . Deceleration is $5 \text{ m/s}^2$ . [2] (b) $v = u + at \Rightarrow 0 = 15 + (-5)t \Rightarrow 5t = 15 \Rightarrow t = 3 \text{ s}$ . [2]

10. (a) The gravitational pull of the book on the Earth. [1] (b) The force of the book pushing down on the table. [1]

11. (a) Distance from pivot = $50 - 10 = 40 \text{ cm} = 0.4 \text{ m}$ . Moment = $F \times d = 2 \times 0.4 = 0.8 \text{ Nm}$ . [2] (b) Principle of Moments: Clockwise Moment = Anticlockwise Moment. $4 \times d = 0.8 \Rightarrow d = 0.2 \text{ m} = 20 \text{ cm}$ . Position = $50 \text{ cm} + 20 \text{ cm} = 70 \text{ cm}$ mark. [2]

12. Pressure = Force / Area. A sharp knife has a very small contact area. For the same applied force, a smaller area results in higher pressure, allowing the knife to penetrate the object easily. [2]

13. (a) $P = h\rho g = 10 \times 1030 \times 10 = 103,000 \text{ Pa}$ . [2] (b) Total Pressure = Atmospheric + Liquid Pressure = $100,000 + 103,000 = 203,000 \text{ Pa}$ . [1]

14. (a) Work Done = Force $\times$ Distance. Force = Weight = $500 \times 10 = 5000 \text{ N}$ . $W = 5000 \times 20 = 100,000 \text{ J}$ . [2] (b) Power = Work / Time = $100,000 / 10 = 10,000 \text{ W}$ (or 10 kW). [2]

15. (a) $KE = \frac{1}{2}mv^2 = 0.5 \times 0.5 \times 10^2 = 0.25 \times 100 = 25 \text{ J}$ . [2] (b) By Conservation of Energy, Max GPE = Initial KE. $mgh = 25 \Rightarrow 0.5 \times 10 \times h = 25 \Rightarrow 5h = 25 \Rightarrow h = 5 \text{ m}$ . [2]

16. (a) The runway is tilted such that the component of weight down the slope exactly balances friction. The trolley moves at constant velocity when given a push. [1] (b) The component of weight down the slope becomes greater than friction. There is a resultant force down the slope, so the trolley accelerates. [1]

17. (a) $P = F/A = 100 / 0.01 = 10,000 \text{ Pa}$ . [2] (b) Pascal's Principle: Pressure is transmitted equally. $F_B = P \times A_B = 10,000 \times 0.1 = 1,000 \text{ N}$ . [2]

18. (a) Mass of the trolley (system). [1] (b) Straight line passing through the origin (positive gradient). [1]

19. (a) Zero. Constant speed implies equilibrium (Newton's 1st Law). [1] (b) Gravitational Potential Energy decreases. Kinetic Energy remains constant (constant speed). The loss in GPE is converted into Internal Energy (Heat) due to work done against friction. [2]

20. (a) Yes. Velocity is a vector (speed + direction). Although speed is constant, the direction is constantly changing. Therefore, velocity changes, which means there is acceleration. [2] (b) Gravitational force (or Gravity). [1]