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CLASS 11
24/8/2015
INDIAN SCHOOL ALWADI ALKABIR
DEPARTMENT OF SCIENCE 2015 -16
PHYSICS
LAWS OF MOTION
NAME:
[1] What force acting on a mass of 15 kg for a minute can change its velocity from 10m/s 2
to 50 m/s2[10N]
[2] A bullet of mass 0.01kg moving with a velocity 100m/s strikes a wooden plank of
thickness 0.5 m, emerges with a velocity 30m/s. Find the resistance offered by the plank,
assuming it to be uniform[91N]
[3] A bullet of mass 20gms. traveling with a velocity of 16 m./s penetrates a sand bag and
is brought to rest in 0.05 s. Find the depth of penetration and the average retarding force of
the sand[0.4 m, 6.4N]
[4] A horizontal force of 500N pulls 2 masses 10kgand 20kg [lying on a frictionless
table]connected by a light string. what is the tension in the string? Does the answer
depend on which mass the pull is being applied?[333.3 N, 166.7N]
[5] 2 objects of masses 3kg and 4Kg are connected by a weightless string which passes
over a frictionless pulley. The objects are initially held at a height of 5 m from the ground
with equal length of the string on either side and then released. Find [a] acceleration of the
system[b] distance between masses 2 seconds after start[1.4m/s2, 5.6m]
[6] A jet of water issuing horizontally at the rate of 10kg/s strikes a vertical wall with a
velocity of 10m/s and rebounds with half the original velocity. what is the force exerted
by the jet on the wall?[150N]
[7] A microphone of mass 0.5 kg hangs from the end of a long wire. A horizontal string
attached to the microphone exerts a pull which keeps the wire at an angle of 20 0 with the
vertical. Find the tensions in the string and the wire.( Ans: 0.5321kgf;0.182 kgf)
[8]A bullet mass 10gm is fired from a gun of mass 8kg with a velocity 160m/s. Find the
velocity of recoil of the gun. Find the force require to stop the gun in a distance of
25cm.[0.64N]
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[9] A block of mass 50 kg is placed on a rough inclined plane. The inclination is
gradually increased to 30° when the block starts sliding down. Find the magnitude of the
limiting friction.[Ans: 245 N)
[10] Derive an expression for the maximum velocity of a vehicle while taking a curve of
radius ‘r’[i] on a level road [ii] on a banked road
[11]Derive the expression for the recoil velocity of a gun
[12]What is impulse and show that impulse = change in momentum
[13]It is easier to push an object than to pull. Explain with the help of a diagram
[14] Stat and prove the law of conservation of momentum
[15] Derive the equation ,F = ma using second law of motion
[16] Which law of motion is said to be real law.Why?
WORK, ENERGY ,POWER
1.At what condition ,work done is negative?
2.work done by the frictional force is negative or positive? .Explain .
3.The force constant of a spring is 50N/m.If a ball of 25gm is shot by the gun sothat the
spring is compressed by 10cm.Calculate the velocity of the ball[1/2kx2 = 1/2mv2]V= √10
4.A person falling on cement floor is likely to receive more injuries than one falling on
loose earth.Why?
5.A man weighing 50kgf carries a load of 1kg on his head. He jumps from the tower with
the load on his head. What will be the weight of the load as experienced by the man?[zero]
6.The momentum of a body is reduced to half. What will be the new kinetic energy?
7.The length of a steel wire increases by 0.5cm, when it is loaded with a weight of
5kg.calculate the force constant of the wire and work done in stretching the wire[g
=10m/s2] w = 0.125J]k = F/x = 5x 10
0.5 x10-2
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W = 1/2Kx2
8.How high must a body be lifted to gain an amount of p.energy equal to the K.E it has
,when moving at speed 20m/s .[g = 9.8m/s2]Ans. 20.4m
9.The force constant of a spring is 60N/m.If abullet of 30gm is shot by the gun ,so that its
spring is compressed by 12cm. calculate the velocity of the ball?[5.36m/s]
10.A gardner moves a lawn roller through a distance of 100m with a force of 50N
.Calculate his wages, if he is to be paid 10 paise for doing 25J of work.It is given that the
applied force is inclined at 600 the direction of motion[10Rs]
W= Fs cosϴ= 2500J,For doing 25J of work ,wage = 10paise
For 1 Joule of work, = 10/ 25 & For 2500J of work = 10/25 x 2500 = 10Rs.
11.Derive the expression to find the final velocities of two bodies after an elastic collision
in1dimensional motion.Discuss the two cases
12. Derive the expression for potential energy of a stretched spring. Show that the law of
conservation of energy is applicable in a spring. Also obtain the maximum velocity of the
spring ,when it crosses the mean position.
13.Derive the expression for kinetic energy and potential energy of body of mass ‘m’
14. State and prove work-energy principle
15. A body of mass 10kg moving with a velocity 20m/s along a straight line, collides with
another body of mass 8kg moving in the same direction with a velocity of 5m,s. After
collision if the final velocity of the former is reduced to16m/s. Calculate the final velocity
of the latter?[10m/s]
Prepared by Mr. William
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