Question:
Why Is it difficult to hold a school bag having strap made of thin and strong string ?
Answer:
We know that pressure = force/area. When the string of the school bag is thin, its area is small and as such the pressure exerted on the shoulders or the hands supporting the bag is large.In this case,the force acting on the shoulders or the hand which support the bag is equal to the weight of the bag.In case,the strap is broad (as is usually the case),the area on which the force (weight of the bag) acts is large and the pressure is reduced (as the weight of the bag is now distributed over a larger area).
Motion
Q 1.
Derive graphically the equation of motion for position-velocity relation of a body moving with uniform acceleration.
Q 2.
A farmer moves along the boundary of a square field of side 10 m in 40 s. What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds?
Q 3.
In addition to speed,what else should be known to predict the position of a moving body from a given starting point ?
Q 4.
Calculate the greatest and the least pressure exerted by a metal block of size 20 cm x 8 cm x 5 cm and having a mass of 5 kg.
Q 5.
What is represented by the graphs in Fig.?
.
Q 6.
What is the relationship between the buoyant force on an object and the liquid displaced by it ?
Q 7.
Under what conditions(s) is the magnitude of average
Q 8.
Air is a fluid and our bodies displace air.As a result of this,a buoyant force is acting on each one of us.
(a)What is the approximate density of your body ?
(b) What is your approximate volume ?
(c) Estimate the magnitude of the buoyant force on you due to the air displaced.Consider your mass to be 75 kg.
(d)Does it mean that your weight is more than the scale reading ?
(Given density of air,pa =
)
Q 9.
Why does a person feel pain when he stands on a pile of gravel than when he stands on a bed of sand ?
Q 10.
An electric train is moving with a velocity of 120 km/h. How much distance will it move in 30 s ?
Q 11.
A body starts from rest.What is zero ?
Q 12.
The density of turpentine oil is
.What will be its relative density ?
Q 13.
A farmer moves along the boundary of a square field of side 10 m in 40 s.What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds ?
Q 14.
Write the three equations of uniformly accelerated motion. Give the meaning of each symbol in them.
Q 15.
Why is a slight blow on a cork of bottle fully filled with a liquid sufficient to break the bottle ?
Q 16.
A cyclist cycles for t second at a speed of 3 m/s and then for the same time at a speed of 5 m/s along a straight road due north. What is the average speed of the cyclist?
Q 17.
What can you calculate from speed-time graph of a body ?
Q 18.
What is the relation between true weight,apparent weight and the loss in weight of a body immersed in a fluid ? Give some practical applications of Archimedes’Principle.
Q 19.
When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Q 20.
What can you say about the motion of an object whose distance-time graph is a straight line parallel to the time axis ?
Q 21.
Name the quantity that represents rate of change of velocity ?
Q 22.
Relative density of silver is 10.8.The density of water is
.What is the density of silver in SI units ?
Q 23.
What will be the initial velocity of an object under free fall?
Q 24.
A particle moves over three quarters of a circle of radius r.What is the magnitude of its displacement ?
Q 25.
Use graphical method to derive the relation
-
= 2 as,where the symbols have their usual meanings.
Q 26.
What does the path of an object look like when it is in uniform motion?
Q 27.
What does the slope of distance-time graph indicate?
Q 28.
Name the terms represented by various symbols in the equation, v = u + at.
Q 29.
Explain the terms : uniform motion and non-uniform motion with examples.
Q 30.
Why is it easier to swim in sea water than in river water ?
Q 31.
A scalar quantity has ?
(a) magnitude only
(b) direction only
(c) both direction and magnitude
(d) none of these
Q 32.
A ship is moving at a speed of 56 km/h.One second later,it is moving at 58 km/h.What is its acceleration ?
Q 33.
Why are sleepers used below the rails ?
Q 34.
A car travels along a straight line for first half time with speed 40 km/h and the second half time with speed 60 km/h. Find the average speed of the car.
Q 35.
What are the values of distance travelled and displacement in covering 10 m from P to Q and coming back ?
Q 36.
The mass of an empty 40 litre petrol tank of a vehicle is 8.0 kg.What will be its mass when filled completely with a fuel of density 700
Q 37.
An object weighs 9.8 N in air and 9.0 N when fully immersed in water.How much is the buoyant force on the object ?
Q 38.
Distinguish between speed and velocity.
Q 39.
A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.
Q 40.
in Fig, shows the distance-time graph of three objects A, B and C. Study the graph and answer the following questions :
(a) Which of the three is travelling the fastest ?
(b)Are ail three ever at the same point on the road ?
(c) How far has C travelled when B passes A ?
(d) How far has B travelled by the time it passes C ?
Q 41.
An artificial satellite is moving in a circular orbit of radius 42250 km. Calculate its speed if it takes 24 hours to revolve around the Earth.
Q 42.
Uniform circular motion is an accelerated motion.Comment
Q 43.
Explain what is meant by uniform circular motion.Give at least three examples.
Q 44.
Puja and Neha are close friends.Puja is a science graduate and Neha is a commerce graduate.Puja finds that while driving on a clear highway,Neha often exceeds the speed limit and agrues that there is no harm in doing so when the road is clear.Puja does not agree with her and tells her that with increase in speed, stopping distance of car would increase and she would not be able to manage things if some stray cattle etc. appears suddenly on the way.Read the above passage and answer the following questions :
(i) Is Puja right in her statement?
(ii) What values are displayed by Puja in her statement?
(iii) How is stopping distance related to speed of vehicle?
Q 45.
A force of 16 N is distributed uniformly on one surface of a cube of edge 8 cm.Find the pressure on this surface.
Q 46.
What is pressure in case of fluids ? What is Pascal’s law ?
Q 47.
The equation v = u + at gives information as
(a) velocity is a function of time.
(b) velocity is a function of position.
(c) Position is a function of time.
(d) Position is function of velocity and time.
Q 48.
Mathematically prove that the distance (S) travelled by an object is the average mean of initial velocity(u) and final velocity(v) having constant acceleration(a) in the direction of motion in a straight line.
Q 49.
Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.
Q 50.
A body starts rolling over a horizontal surface with an initial velocity of 0.5
.Due to friction,its velocity decreases at the rate of 0 05
.How much time will it take for the body to stop ?
