Question:
Why is it easier to swim in sea water than in river water ?
Answer:
Sea water is heavier than river water (density of sea water is around ).Thus,the immersed portions of the body of a swimmer experience greater buoyancy in sea water than in river water.
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.
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 4.
What can you calculate from speed-time graph of a body ?
Q 5.
Why does a person feel pain when he stands on a pile of gravel than when he stands on a bed of sand ?
Q 6.
A body starts from rest.What is zero ?
Q 7.
When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Q 8.
What does the path of an object look like when it is in uniform motion?
Q 9.
What is represented by the graphs in Fig.?
.
Q 10.
Relative density of silver is 10.8.The density of water is
.What is the density of silver in SI units ?
Q 11.
In addition to speed,what else should be known to predict the position of a moving body from a given starting point ?
Q 12.
What is the relationship between the buoyant force on an object and the liquid displaced by it ?
Q 13.
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 14.
A train 100 m long moving on a straight level track passes a pole in 5 s. Find (a) the speed of the train (b) the time it will take to cross a bridge 500 m long.
Q 15.
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 16.
What will be the initial velocity of an object under free fall?
Q 17.
What can you say about the motion of an object whose distance-time graph is a straight line parallel to the time axis ?
Q 18.
Why is it easier to swim in sea water than in river water ?
Q 19.
Distinguish between speed and velocity.
Q 20.
Under what conditions(s) is the magnitude of average
Q 21.
What are the values of distance travelled and displacement in covering 10 m from P to Q and coming back ?
Q 22.
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 23.
An electric train is moving with a velocity of 120 km/h. How much distance will it move in 30 s ?
Q 24.
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 25.
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 26.
Can displacement and distance ever be equal ?
Q 27.
Use graphical method to derive the relation
-
= 2 as,where the symbols have their usual meanings.
Q 28.
Draw speed-time graph for a body (i) at rest (ii) in uniform motion (iii) in uniformly accelerated motion.Discuss the results briefly.
Q 29.
Name the quantity that represents rate of change of velocity ?
Q 30.
What conclusion do you draw when displacement-time graph of a body is as shown in Fig.?
Q 31.
What do the graphs shown in Fig.indicate?
Q 32.
Write the three equations of uniformly accelerated motion. Give the meaning of each symbol in them.
Q 33.
A block of wood is kept on a table top.The mass of the wooden block is 5 kg and its dimensions are 40 cm x 20 cm x 10 cm.Find the pressure exerted by the wooden block on the table top if it is made to lie on the table with its sides of dimensions (a) 20 cm x 10 cm (b) 40 cm x 20 cm. Given g =
.
Q 34.
The density of turpentine oil is
.What will be its relative density ?
Q 35.
Why are sleepers used below the rails ?
Q 36.
Under what condition(s) is the magnitude of average velocity of an object equal to its average speed?
Q 37.
Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.
Q 38.
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 39.
A particle moves over three quarters of a circle of radius r.What is the magnitude of its displacement ?
Q 40.
Explain the terms : uniform motion and non-uniform motion with examples.
Q 41.
Derive graphically the equation v=u + at,where the symbols have their usual meanings.
Q 42.
A stone tied to one end of a string is rotated in a circle.Explain what happens when the stone is released.
Q 43.
Why Is it difficult to hold a school bag having strap made of thin and strong string ?
Q 44.
Why is a slight blow on a cork of bottle fully filled with a liquid sufficient to break the bottle ?
Q 45.
What is thrust ?How is it related to pressure ? Give their units.
Q 46.
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 47.
An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.
Q 48.
Are motion and rest absolute or relative? Explain with an example.
Q 49.
What does the odometer of an automobile measure?
Q 50.
A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.
