1x5=5
Answer the following
1. Define static friction.
2. Write the SI unit of coefficient of kinetic friction.
3. What is meant by equilibrium of a particle?
4. What is banking of roads?
5. Give the graphical representation of applied force and frictional force.
Answer the following
2x2=4
6. Mention any two examples where friction is a necessity.
7. What is limiting friction? Write an expression for force of limiting friction.
Answer the following
2x3=6
8. Mention any three methods of reducing friction.
9. Derive the expression for maximum speed of circular motion of a car on a level road.
1x5=5
Answer the following
10. State and prove the law of conservation oflinear momentum.
1x5=5
Answer the following
11. A bullet of mass 0.04 kg moving with a speed of 90 m/s enters a heavy block and is stopped
after a distance of 0.6 m. What is the average resistive force exerted by the block on the
bullet.
IV.
V.
Answers
1)In friction. Static friction, in contrast, acts between surfaces at rest with respect to each other. The value of static friction varies between zero and the smallest force needed to start motion. This smallest force required to start motion, or to overcome static friction, is always greater…
2)As we know the units of force are newton and normal is also a force, hence its unit is also newton. The two forces units will cancel each other. Therefore, the coefficient of friction has no unit. It is a unit less and dimensionless quantity
3)According to Newton's first law, a particle is said to be in equilibrium if. there is no net force acting on it. This does not mean that no forces act on. the particle, but rather that the resultant of all the forces which do act on. the particle is zero
4)Banking of roads is defined as the phenomenon in which the edges are raised for the curved roads above the inner edge to provide the necessary centripetal force to the vehicles so that they take a safe turn. ... The angle at which the vehicle is inclined is defined as the bank angle.
5)The frictional force opposing the motion of the crate is equal to the applied force but acting in the opposite direction. This frictional force is called static friction. When we increase the applied force (push harder), the frictional force will also increase until it reaches a maximum value.
6)The examples to illustrate that friction is a necessary evil are: If friction were absent, we would not be able to walk. Friction is necessary to burn a matchstick. It is due to friction that we can write on a board by a chalk.
7)The maximum friction that can be generated between two static surfaces in contact with each other. Once a force applied to the two surfaces exceeds the limiting friction, motion will occur. For two dry surfaces, the limiting friction is a product of the normal reaction force and the coefficient of limiting friction.
8)
Make the surfaces smoother. Rough surfaces produce more friction and smooth surfaces reduce friction.
Lubrication is another way to make a surface smoother. ...
Make the object more streamlined. ...
9)
10)According to the law of conservation of linear momentum, for an object or system of objects, the total momentum of the system is always conserved if no external force acts on them. The unit of kg.m.s-1 and the dimensional formula is MLT-1.
11)answr
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11th
Physics
Motion in a Straight Line
Problems on Equation of Motion
A bullet of mass 0.04 kg mo...
PHYSICS
A bullet of mass 0.04 kg moving with a speed of 90m/s enters a heavy wooden block and is stopped after a distance of 60 cm . What is the average force exerted by the block on the bullet?
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ANSWER
Given,
m=0.04kg
u=90m/s
v=0m/s
S=60cm
From 3rd equation of motion,
2aS=v
2
−u
2
a=−
2S
u
2
a=−
2×60×10
−2
90×90
=−6750m/s
2
The resistive force, f=ma
f=−0.04×67.5
f=−270N