Question:
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.
Answer:
Refer to Arts.4.10 and 4.12,Pages 228,230.
Motion
Q 1.
Derive graphically the equation of motion for position-velocity relation of a body moving with uniform acceleration.
Q 2.
What can you calculate from speed-time graph of a body ?
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.
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 5.
Distinguish between speed and velocity.
Q 6.
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 7.
Under what conditions(s) is the magnitude of average
Q 8.
Why is it easier to swim in sea water than in river water ?
Q 9.
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 10.
When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Q 11.
Are motion and rest absolute or relative? Explain with an example.
Q 12.
What does the path of an object look like when it is in uniform motion?
Q 13.
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 14.
What is represented by the graphs in Fig.?
.
Q 15.
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 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.
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 18.
Can displacement and distance ever be equal ?
Q 19.
A particle moves over three quarters of a circle of radius r.What is the magnitude of its displacement ?
Q 20.
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 21.
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 22.
The density of turpentine oil is
.What will be its relative density ?
Q 23.
What does the slope of distance-time graph indicate?
Q 24.
What do the graphs shown in Fig.indicate?
Q 25.
Why is a slight blow on a cork of bottle fully filled with a liquid sufficient to break the bottle ?
Q 26.
Why are sleepers used below the rails ?
Q 27.
An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.
Q 28.
A scalar quantity has ?
(a) magnitude only
(b) direction only
(c) both direction and magnitude
(d) none of these
Q 29.
The speed-time graph for a car is shown is Fig.
(a) Find how far does the car travel in the first 4 seconds.Shade the area on the graph that represents the distance travelled by the car during this period.
(b) Which part of the graph represents uniform motion of the car ?
.
Q 30.
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 31.
A train is running at a speed of 72 km/h. It crosses a bridge of length half kilometer in 1 minute. Calculate the length of the train.
Q 32.
Fig (below) 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 all 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 33.
A body thrown vertically upwards reaches a maximum height h.It then returns to ground.Calculate the distance travelled and the displacement.
Q 34.
Name the quantity that represents rate of change of velocity ?
Q 35.
A body starts from rest.What is zero ?
Q 36.
The mass of a solid rectangular block of iron is 23.6 g and its dimensions are 2.1 cm x 1.2 cm x 1.1 cm.Calculate the density of iron.
Q 37.
The mass of a density bottle is 25 g when empty, 50 g when filled completely with water and 365 g when filled completely with mercury. Find the density of mercury.
Q 38.
A particle moves along the x axis from A to B. Which Of the following values of the initial and final coordinates, which results in a negative displacement?
(a) A = 4m, B = 6m
(b) A = −4m, B = −2m
(c) A = −4m, B = −8m
(d) A = −4m, B = 2m
Q 39.
A racing car has a uniform acceleration of 4 m s–2.
What distance will it cover in 10 s after start?
Q 40.
Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.
Q 41.
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 ?
Q 42.
A body is moving uniformly with a velocity of 5 m/s. Find graphically the distance travelled by it in 5 s.
Q 43.
A racing car has uniform acceleration of
.What distance will it cover in 10 seconds after start ?
Q 44.
A car accelerates uniformly from 18 km/h to 36 km/h in 5 second. Calculate (i) the acceleration and (ii)the distance covered by the car in that time.
Q 45.
What can you say about the motion of an object whose distance-time graph is a straight line parallel to the time axis ?
Q 46.
A stone is thrown in a vertically upward direction with a velocity of 5 m/s. If the acceleration of the stone during its motion is
in the downward direction,what will be the height attained by the stone and how much time will it take to reach there ?
Q 47.
Is displacement a scalar quantity ?
Q 48.
Is distance a vector quantity ?
Q 49.
What is SI unit of speed ? Is it same for velocity ?
Q 50.
What changes continuously in uniform circular motion ?
