APEEJAY SCHOOL, SAKET FIRST TERM EXAMINATION (2018-19) CLASS-XI PHYSICS

Time: 3 Hours

Max. Marks: 70

GENERAL INSTRUCTIONS

All questions are compulsory.

The question paper consists of 27 questions.

The question paper has four sections: Section A comprises 5 Questions (1 marks each), Section B comprises 7 Questions (2 marks each), Section C comprises 12 Questions (3 marks each) and Section D comprises 3 Questions (5 marks each).

1. Questions from Section A are to be answered in one word or one sentence as per requirement.

Calculator is not permitted. You may ask for logarithm table if required.

SECTION – A

Find the dimensional formula of coefficient of viscosity (η). (1)

Give an example of uniformly accelerated linear motion. (1)

1. What is the value of m in <math>i + mj + k</math> to be unit vector? (1)

What is the loss in kinetic energy after collision if the target of a body is initially at rest?(1)

1. Does the moment of inertia of a rigid body change with the speed of rotation? (1)

SECTION – B

Write the dimensions of (a) Moment of Inertia (b) Stress and Strain. (2)

<math>\mathbf{OR}</math>

Using the relation, obtain the dimensions of Planck's constant.

1. Find the angle of projection at which horizontal range and maximum height are equal in case

of a projectile. (2)

A woman throws an object of mass 500 g with a speed of 25 m/s.

1. What is the impulse imparted to the object?
2. If the object hits a wall and rebounds with half the original speed, what is the change in momentum of the object? (2)
3. A spring balance reads forces in Newtons. The scale is 20 cm long and read from 0 to 60 N. Find the potential energy of spring when the scale reads 20 N. (2)
4. If the earth contracts to half of its radius. What would be the length of the day? (2)
5. In HCl molecule separation of nuclei of the two atoms is about 1.27 Å. Find the centre of mass of molecule given that chlorine atom is about 35.5 times massive than a hydrogen atom.

(2)

1. Determine the speed with which the earth would have to rotate on its axis so that a person on

the equator would weigh 3/5th as much as his weight at present. Take the equatorial radius as 6400 km. (2)

SECTION – D

1. The speed-time graph of a particle moving along a fixed direction is shown in the figure

below. Obtain the distance travelled by the particle between (i) <math>t = 0</math> s to 10 s (ii) <math>t = 2</math> s to 6 s. What is the average speed of the particle over the intervals in (i) and (ii)? (5)

Speed v (m/s) 12 <math>\boldsymbol{c}</math> - t(s) 5 10 OR Show that for motion of a car in a banked road the angle of banking <math>\theta</math> for minimum wear and tear of tyres is given by where v is the velocity, r is the radius and g is acceleration due to gravity.

1. Show that the path of projectile is parabolic in nature using right expression. Derive an

expression of horizontal range of projectile. (5) OR A particle of mass m moving with an initial velocity u collides inelastically with a particle of mass M initially at rest. If the collision is completely inelastic, find the expressions for

final velocity of the combined entity and

loss in kinetic energy during collision.

1. Choose the correct alternatives : (Substantiate your answers with suitable explanation)
2. Acceleration due to gravity increase / decreases with increasing altitude. (5)
3. Acceleration due to gravity increase / decreases with increasing depth( assuming earth to be uniform sphere)
4. Acceleration due to gravity is independent of mass of the earth / mass of the body.
5. The formula is more / less accurate than the formula )for the difference of potential energy between two points and distance away from centre of earth.

<math>\mathbf{OR}</math>

Find the centre of mass for a solid cone of the base radius r and height h.