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.
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 2.
Derive graphically the equation of motion for position-velocity relation of a body moving with uniform acceleration.
Q 3.
What can you calculate from speed-time graph of a body ?
Q 4.
When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Q 5.
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 6.
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 7.
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 8.
A body starts from rest.What is zero ?
Q 9.
Why is it easier to swim in sea water than in river water ?
Q 10.
Why does a person feel pain when he stands on a pile of gravel than when he stands on a bed of sand ?
Q 11.
What is represented by the graphs in Fig.?
.
Q 12.
Distinguish between speed and velocity.
Q 13.
Under what conditions(s) is the magnitude of average
Q 14.
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 15.
Can displacement and distance ever be equal ?
Q 16.
In addition to speed,what else should be known to predict the position of a moving body from a given starting point ?
Q 17.
What are the values of distance travelled and displacement in covering 10 m from P to Q and coming back ?
Q 18.
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 19.
Relative density of silver is 10.8.The density of water is
.What is the density of silver in SI units ?
Q 20.
What does the odometer of an automobile measure?
Q 21.
What does the path of an object look like when it is in uniform motion?
Q 22.
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 23.
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 24.
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 25.
The density of turpentine oil is
.What will be its relative density ?
Q 26.
A body thrown vertically upwards reaches a maximum height h.It then returns to ground.Calculate the distance travelled and the displacement.
Q 27.
Write the three equations of uniformly accelerated motion. Give the meaning of each symbol in them.
Q 28.
An iron sphere is suspended with a spring.The length of the spring increases.When the sphere is completely in water,the extension in the length of the spring decreases.Why does it happen so ?
Q 29.
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 30.
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 31.
What will be the initial velocity of an object under free fall?
Q 32.
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 33.
An electric train is moving with a velocity of 120 km/h. How much distance will it move in 30 s ?
Q 34.
What can you say about the motion of an object whose distance-time graph is a straight line parallel to the time axis ?
Q 35.
Is distance a vector quantity ?
Q 36.
A particle moves over three quarters of a circle of radius r.What is the magnitude of its displacement ?
Q 37.
Use graphical method to derive the relation
-
= 2 as,where the symbols have their usual meanings.
Q 38.
Draw speed-time graph for a body (i) at rest (ii) in uniform motion (iii) in uniformly accelerated motion.Discuss the results briefly.
Q 39.
What is thrust ?How is it related to pressure ? Give their units.
Q 40.
Why are sleepers used below the rails ?
Q 41.
An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.
Q 42.
Under what condition(s) is the magnitude of average velocity of an object equal to its average speed?
Q 43.
A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.
Q 44.
A scalar quantity has ?
(a) magnitude only
(b) direction only
(c) both direction and magnitude
(d) none of these
Q 45.
A driver of a car travelling at 52 km/h applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 3 km/h in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?
Q 46.
The speed-time graph for a car is shown is figure below.
(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 the period.
(b) Which part of the graph represents uniform motion of the car?
Q 47.
Fill in the blanks :
If the position of an object does not change with time, it is said to be at _____.
Q 48.
Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.
Q 49.
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 50.
A scooter acquires a velocity of 36 km/h in 10 seconds just after the start.Calculate the acceleration of the scooter.
