Question:
Why do objects float or sink when placed on the surface of a liquid ?
Answer:
Refer to Art.4.9,Page 227.
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.
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 3.
When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Q 4.
Derive graphically the equation of motion for position-velocity relation of a body moving with uniform acceleration.
Q 5.
Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.
Q 6.
A body thrown vertically upwards reaches a maximum height h.It then returns to ground.Calculate the distance travelled and the displacement.
Q 7.
Why are sleepers used below the rails ?
Q 8.
Are motion and rest absolute or relative? Explain with an example.
Q 9.
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 10.
Fill in the blanks :
If the position of an object does not change with time, it is said to be at _____.
Q 11.
Can displacement and distance ever be equal ?
Q 12.
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 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.
What does the path of an object look like when it is in uniform motion?
Q 15.
What does the slope of distance-time graph indicate?
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.
Why is a slight blow on a cork of bottle fully filled with a liquid sufficient to break the bottle ?
Q 18.
Discuss three important practical aspects of pressure related to daily life.
Q 19.
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 20.
A body starts to slide over a horizontal surface with an initial velocity of 0-5 m/s. Due to friction, its velocity decreases at the rate of 0.05
.How much time will it take for the body to stop ?
Q 21.
Draw speed-time graph for a body (i) at rest (ii) in uniform motion (iii) in uniformly accelerated motion.Discuss the results briefly.
Q 22.
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 23.
Relative density of silver is 10.8.The density of water is
.What is the density of silver in SI units ?
Q 24.
Define buoyant force.What is its unit ?
Q 25.
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 26.
What is meant by scalars and vectors?
Q 27.
What does the odometer of an automobile measure?
Q 28.
A train is travelling at a speed of 90 kmh–1. Brakes are applied so as to produce a uniform acceleration of – 0.5 ms–2. Find how far the train will go before it is brought to rest.
Q 29.
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 30.
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 31.
Can distance be negative ?
Q 32.
What is SI unit of speed ? Is it same for velocity ?
Q 33.
What is the acceleration of a body moving with uniform velocity ?
Q 34.
If velocity-time graph of a body is as shown in Fig.,what is the nature of motion ?
Q 35.
Use graphical method to derive the relation
-
= 2 as,where the symbols have their usual meanings.
Q 36.
Draw distance-time graph for a body (i) at rest (ii) in uniform motion (iii) in non-uniform motion.Discuss their interpretation.
Q 37.
Calculate the pressure when a force of 200 N acts on an
Q 38.
What is the density of water at 4°C ?
Q 39.
State Archimedes’ Principle ? What is the relation between true weight,apparent weight and the buoyant force ?
Q 40.
Breathing is the process that moves air in (inhaling) and out (exhaling) of the lungs.Breath is life as breathing provides 99% of energy to our bodies.
(a) What happens when we inhale ?
(b)Why a person with pulmonary disease has difficulty in breathing ?What message does it convey ?
(c) What is done to make a newborn have his first breath ?
Q 41.
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 42.
Distinguish between speed and velocity.
Q 43.
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 44.
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 45.
A particle is moving in a circle of diameter 5 m. Calculate the distance covered and the displacement when it completes 3 revolutions.
Q 46.
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 47.
A train starting from rest moves with a uniform acceleration of 0.2
for 5 minutes.Calcualte the speed acquired and the distance travelled in this time.
Q 48.
Under what conditions(s) is the magnitude of average
Q 49.
When will you say a body is in (») uniform acceleration ? (ii) non-uniform acceleration ?
Q 50.
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 ?
