NCERT Class 11 Physics Laws of Motion

NCERT Class 11 Physics Laws of Motion with answers available in Pdf for free download. The NCERT Solutions for Class 11 Physics with answers have been prepared as per the latest syllabus, NCERT books and examination pattern suggested in Standard 11 by CBSE, NCERT and KVS. Solutions to questions given in NCERT book for Class 11 Physics are an important part of exams for Grade 11 Physics and if practiced properly can help you to get higher marks. Refer to more Chapter-wise Solutions for NCERT Class 11 Physics and also download more latest study material for all subjects

Laws of Motion Class 11 NCERT Solutions

Class 11 Physics students should refer to the following NCERT questions with answers for Laws of Motion in standard 11. These NCERT Solutions with answers for Grade 11 Physics will come in exams and help you to score good marks

Laws of Motion NCERT Solutions Class 11

NCERT Class 11 Physics Laws of Motion - NCERT Solutions prepared for CBSE students by the best teachers in Delhi.  Check out this link also - class 11 physics syllabus.

Class XI Physics

Ch. 5: Laws of Motion

NCERT Solutions

 

Question 5.1:

Give the magnitude and direction of the net force acting on

(a) a drop of rain falling down with a constant speed,

(b) a cork of mass 10 g floating on water,

(c) a kite skillfully held stationary in the sky,

(d) a car moving with a constant velocity of 30 km/h on a rough road,

(e) a high-speed electron in space far from all material objects, and free of electric and magnetic fields.

ANS:

(a) Zero net force

   The rain drop is falling with a constant speed. Hence, it acceleration is zero. As per Newton’s second law of motion, the net force acting on the rain drop is zero.

(b) Zero net force

   The weight of the cork is acting downward. It is balanced by the buoyant force exerted by the water in the upward direction. Hence, no net force is acting on the floating cork.

(c) Zero net force

   The kite is stationary in the sky, i.e., it is not moving at all. Hence, as per Newton’s first law of motion, no net force is acting on the kite.

(d) Zero net force

   The car is moving on a rough road with a constant velocity. Hence, its acceleration is zero. As per Newton’s second law of motion, no net force is acting on the car.

(e) Zero net force

   The high speed electron is free from the influence of all fields. Hence, no net force is acting on the electron.

Question 5.2:

A pebble of mass 0.05 kg is thrown vertically upwards. Give the direction and magnitude of the net force on the pebble,

   (a) during its upward motion,

   (b) during its downward motion,

   (c) at the highest point where it is momentarily at rest. Do your answers change if the pebble was thrown at an angle of 45° with the horizontal direction? Ignore air resistance.

ANS: 0.5 N, in vertically downward direction, in all cases Acceleration due to gravity, irrespective of the direction of motion of an object, always acts downward. The gravitational force is the only force that acts on the pebble in all three cases. Its magnitude is given by Newton’s second law of motion

   as:

   F  = m × a

   Where, F = Net force

   m = Mass of the pebble = 0.05 kg

   a = g = 10 m/s2

   ∴F = 0.05 × 10 = 0.5 N 

The net force on the pebble in all three cases is 0.5 N and this force acts in the downward direction. If the pebble is thrown at an angle of 45° with the horizontal, it will have both the horizontal and vertical components of velocity. At the highest point, only the vertical  component of velocity becomes zero. However, the pebble will have the horizontal component of velocity throughout its motion. This component of velocity produces no effect on the net force acting on the pebble.

Question 5.3:

Give the magnitude and direction of the net force acting on a stone of mass 0.1 kg,

(a) just after it is dropped from the window of a stationary train,

(b) just after it is dropped from the window of a train running at a constant velocity of 36 km/h,

(c) just after it is dropped from the window of a train accelerating with 1 m s–2,

(d) lying on the floor of a train which is accelerating with 1


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Click for more Physics Study Material
Chapter 2 Units and Measurement
NCERT Class 11 Physics Solutions Units and Measurements
Chapter 4 Motion in a Plane
NCERT Class 11 Physics Motion in a Plane
Chapter 5 Laws of Motion
NCERT Class 11 Physics Laws of Motion
Chapter 6 Work Energy and Power
NCERT Class 11 Physics Work Power Energy
Chapter 7 System of Particles and Rotational Motion
NCERT Class 11 Physics System of particles and rotational motion
Chapter 8 Gravitation
NCERT Class 11 Physics Gravitation
Chapter 9 Mechanical Properties of Solids
NCERT Class 11 Physics Mechanical Properties of solids
Chapter 10 Mechanical Properties of Fluids
NCERT Class 11 Physics Mechanical Properties of Fluids
Chapter 11 Thermal Properties of Matter
NCERT Class 11 Physics Thermal properties of matter
Chapter 12 Thermodynamics
NCERT Class 11 Physics Thermodynamics
Chapter 13 Kinetic Theory
NCERT Class 11 Physics Kinetic Theory
Chapter 14 Oscillations
NCERT Class 11 Physics Oscillations
Chapter 15 Waves
NCERT Class 11 Physics Waves

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