15 extra multiple-choice questions for Laws of Motion (10th Standard Science, Samacheer Kalvi), beyond the ones printed in the textbook — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
Which branch of mechanics deals with the study of moving bodies without considering the cause of their motion?
- A. Statics
- B. Kinetics
- C. KinematicsCorrect
- D. Dynamics
Explanation. Kinematics is the branch of mechanics that deals with the motion of bodies without considering the cause of their motion, while kinetics considers the cause of motion.
Q2
According to the Greek philosopher Aristotle, what is the term used to describe a force-independent motion where a moving body naturally comes to rest?
- A. Natural motionCorrect
- B. Violent motion
- C. Inertial motion
- D. Unbalanced motion
Explanation. Aristotle stated that natural motion is force-independent, meaning a moving body naturally comes to rest without any external influence of force.
Q3
According to Galileo's concepts, what happens when different bodies of different size, shape, and mass are dropped from a height in vacuum?
- A. The heavier body falls faster than the lighter body.
- B. They fall at the same rate and reach the ground at the same time.Correct
- C. The lighter body falls faster due to less resistance.
- D. They remain suspended because there is no gravity in vacuum.
Explanation. Galileo proposed that in vacuum, all bodies of different size, shape, and mass fall at the same rate and reach the ground at the same time.
Q4
When a passenger in a moving vehicle tends to lean sideways during a sharp turn, which type of inertia is being demonstrated?
- A. Inertia of rest
- B. Inertia of motion
- C. Inertia of directionCorrect
- D. Inertia of mass
Explanation. The resistance of a body to change its direction of motion is known as inertia of direction, which causes the passenger to lean sideways during a turn.
Q5
What is the unit of linear momentum in the C.G.S system?
- A. kg m s-1
- B. g cm s-1Correct
- C. N s
- D. dyne s
Explanation. Linear momentum is the product of mass and velocity. In the C.G.S system, mass is in grams and velocity is in cm s-1, giving g cm s-1.
Q6
Newton's first law of motion provides the scientific definitions for which of the following concepts?
- A. Force and InertiaCorrect
- B. Mass and Acceleration
- C. Momentum and Friction
- D. Gravity and Weight
Explanation. Newton's first law states that every body continues in its state of rest or uniform motion unless acted on by an external force, defining both force and inertia.
Q7
Two parallel unequal forces of 15 N and 5 N act in opposite directions on a body. What is the net resultant force and its direction?
- A. 20 N in the direction of the 15 N force
- B. 10 N in the direction of the 15 N forceCorrect
- C. 10 N in the direction of the 5 N force
- D. 0 N since the forces are in opposite directions
Explanation. Since the forces are unequal, parallel, and act in opposite directions, the resultant force is their difference, 10 N, directed along the greater 15 N force.
Q8
A door is pushed, at a point whose distance from the hinges is 90 cm, with a force of 40 N. Calculate the moment of the force about the hinges.
- A. 3.6 N m
- B. 36 N mCorrect
- C. 360 N m
- D. 3600 N m
Explanation. The moment of force is calculated as force multiplied by perpendicular distance from hinges. Hence, 40 N multiplied by 0.9 m equals 36 N m.
Q9
Because Newton's second law of motion helps us measure the amount of force acting on a body, it is also known as the:
- A. Law of inertia
- B. Law of forceCorrect
- C. Law of moments
- D. Law of momentum
Explanation. Newton's second law states that force is directly proportional to the rate of change of linear momentum. Because it measures force, it is called the law of force.
Q10
In a uniform circular motion, even though the speed of the body remains constant, the direction of velocity changes at every point. What is the direction of the resulting centripetal acceleration?
- A. Tangential to the circular path
- B. Along the radius, pointing away from the center
- C. Along the radius, pointing toward the centerCorrect
- D. Opposite to the direction of motion
Explanation. In uniform circular motion, the acceleration produced by the changing velocity direction acts along the radius toward the center, called centripetal acceleration.
Q11
Which of the following describes the definition of 1 dyne of force in the C.G.S system?
- A. The force that produces an acceleration of 1 m s-2 in a mass of 1 g
- B. The force that produces an acceleration of 1 cm s-2 in a mass of 1 kg
- C. The force that produces an acceleration of 1 cm s-2 in a mass of 1 gCorrect
- D. The force that produces an acceleration of 9.8 m s-2 in a mass of 1 g
Explanation. One dyne is the amount of force that produces an acceleration of 1 cm s-2 when acting on a mass of 1 g.
Q12
Under what condition is the algebraic sum of the linear momentum of a system of colliding bodies conserved?
- A. Only if the collision is perfectly elastic
- B. In the absence of an external net forceCorrect
- C. Only if the masses of the bodies are equal
- D. If the temperature of the system remains constant
Explanation. According to the principle of conservation of linear momentum, the total linear momentum of a system is conserved as long as no net external force acts on it.
Q13
What is the value and SI unit of the universal gravitational constant (G)?
- A. \(6.674 x 10^-11 N m2\) kg-2Correct
- B. \(6.674 x 10^-11 N m\) kg-2
- C. 9.8 m s-2
- D. \(6.674 x 10^-11\) dyne cm2 g-2
Explanation. The universal gravitational constant G has a constant value of \(6.674 x 10^-11 N m2\) kg-2 in the SI system.
Q14
What is the apparent weight (R) of a person of mass m in a lift that is at rest or moving with uniform velocity?
- A. R = m(g + a)
- B. R = m(g - a)
- C. R = mgCorrect
- D. R = 0
Explanation. When the lift is at rest or moving with uniform velocity, acceleration 'a' is zero, so the apparent weight is equal to the actual weight, R = mg.
Q15
Why do astronauts in an orbiting space shuttle experience weightlessness?
- A. Because there is no gravity in the orbit of the space shuttle
- B. Because they and the space shuttle are in a state of free fall under gravityCorrect
- C. Because the centrifugal force completely neutralizes gravity
- D. Because the mass of the astronauts becomes zero in space
Explanation. Both the astronauts and the space shuttle fall freely around the Earth with equal acceleration, so they are in a state of free fall, experiencing weightlessness.
