## Saturday, 14 January 2017

### CBSE CLASS11 MIDTERM PHYSICS PAPER

1.The wheels of vehicles are provided with mudguards. Why?
2. Define spring constant of a spring?
3. What happens to the P.E of a bubble when it rises in water?
4. A light and a heavy body have same K.E. which of the two have more momentum and why?
5. The position x of a body of mass 2 kg varies with time t as x = (2t2 + 3t – 4) m.Find  Force acting on the
body
6. A body of mass 2kg moving with a speed of 100 m/s hits a wall and rebounds with the same speed. If
the contact time is (1/50)s,Find the force applied on the wall
7. A body dropped from a height H reaches the ground with a speed of 1.m/s2. Calculate the work done
by air-friction.
8. A light string passes over a frictionless pulley. To one of its ends a mass of 6 kg is attached and
to its other end a mass of 10 kg is attached. Find tension in the string .
9. A hunter has a machine gun that can fire 50g bullets with a velocity of 150 ms–1. A 60 kg tiger springs
at him with a velocity of 10 ms–1 How many bullets must the hunter fire into the target so as to stop
him in his track?
10. A bullet of mass 0.01 kg is fired horizontally into a 4 kg wooden block at rest on a horizontal surface.
The coefficient of kinetic friction between the block and the surface is 0.25. The bullets gets
embedded in the block and the combination moves 20m before coming to rest. With what speed
did the bullet strike the block?
11. You push your physics book 1.50 m along a horizontal tabletop with a horizontal push of 2.40 N
while  the opposing force    of friction is 0.600 N. How much work does each of the following forces
do on the   book: (a) your 2.40-N push, (b) the   friction force, (c) the normal force from the tabletop,
and (d) gravity? (e) What is the net work done on the book?
12.  Your job is to lift 30-kg crates a vertical distance of 0.90 m from the ground onto the bed of a
truck.(a) How many crates would you have to load onto the truck in1 minute for the average power
output you use to lift the crates  to equal 0.50 hp? (b) How many crates for an average power output
of 100 W

13.How does a perfectly inelastic collision differ from perfectly elastic collision? Two particles of
mass  m1 and m2 having velocities u1 and u2 respectively make a head on collision. Derive the
relation for  their finalvelocities. Discuss the following special cases.
(i) m1 = m2 (ii) m1 >> m2 and U2 = 0  (iii) m1 << m2 and u1 = 0
OR
The blades of a windmill sweep out a circle of area A a) If the wind flows at a velocity v perpendicular
to the circle, what is the mass of the air passing through it in time t?
b)What is the kinetic energy of the air? (c) Assume that the windmill converts 25% of the wind’s
energy into electrical energy, and that A = 30m2 , v = 36km/hr and density of air is 1.2 kg   m–3.         What   is the electrical power produced?
14.A disc revolves with a speed of 33 rev/min and has a radius of 15cmTwo coins are placed at 4
cm    and 14 cm away from the centre of the record. If the coefficient of friction between the coins
and  the record is 0.15, which of the coins will revolve with the record?
OR
Why circular roads are banked? Derive an expression for maximum possible speed with which
angle of banking is needed for safe circular turn