Question:
What changes continuously in uniform circular motion ?
Answer:
Velocity of the body changes continuously in uniform circular motion.
Motion
Q 1.
Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.
Q 2.
What do you mean by a body in rest?
Q 3.
What changes continuously in uniform circular motion ?
Q 4.
Which of the following is true for displacement?
(a) It cannot be zero.
(b) Its magnitude is greater than the distance travelled by the object.
Q 5.
The equation S = ut + ½at2 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 6.
Derive graphically the equation v=u + at,where the symbols have their usual meanings.
Q 7.
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 8.
A cube of edge length 10 cm is placed inside a liquid.The pressure at the centre of the face is 15 Pa.Find the force exerted by the liquid on this face.
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.
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 11.
The density of turpentine oil is
.What will be its relative density ?
Q 12.
Uniform circular motion is an accelerated motion.Comment
Q 13.
A force of 100 N is applied on an object of area
.Calculate the pressure.
Q 14.
Why is it easier to swim in sea water than in river water ?
Q 15.
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 16.
A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.
Q 17.
Draw distance-time graph for a body (i) at rest (ii) in uniform motion (iii) in non-uniform motion.Discuss their interpretation.
Q 18.
Write the three equations of uniformly accelerated motion. Give the meaning of each symbol in them.
Q 19.
A body thrown vertically upwards reaches a maximum height h.It then returns to ground.Calculate the distance travelled and the displacement.
Q 20.
A train travels some distance with a speed of 30 km/h and returns with a speed of 45 km/h.Calculate the average speed of the train.
Q 21.
Use graphical method to derive the relation
-
= 2 as,where the symbols have their usual meanings.
Q 22.
Draw speed-time graph for a body (i) at rest (ii) in uniform motion (iii) in uniformly accelerated motion.Discuss the results briefly.
Q 23.
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 24.
What is represented by the graphs in Fig.?
.
Q 25.
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 26.
A motor cycle moving with a speed of 5 m/s is subjected to an acceleration of 0.2
.Calculate the speed of the motor cycle after 10 second,and the distance travelled in this time.
Q 27.
A trolley, while going down an inclined plane, has an acceleration of
starting from rest.What will be its velocity 3 s after the start ?
Q 28.
What can you calculate from speed-time graph of a body ?
Q 29.
A Physics teacher is explaining the difference between average speed and average velocity to her students.
She emphasises that average speed is more relevant than average velocity,because displacement from one place to other is only theoretical, being the shortest distance between two places. Average speed is the real entity that matters,taking into account the actual time taken to travel the actual distance between the two stations.
Read the above passage and answer the following questions :
(i) Do you agree with the statement of Physics teacher?
(ii) The shortest distance between Ambala and Delhi is 200 km.A train takes 4 hrs and covers a distance of 210 km in going from Ambala to Delhi via Karnal.Another train takes 5 hrs and covers 250 km distance in going from Ambala to Delhi via Saharanpur.What is the average speed of these two trains ? What would be the average velocity of a train that takes 2.5 hrs to cover 200 km distance ?
(iii) What values do you learn from this discussion ?
Q 30.
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 31.
Calculate the mass of a body whose volume is
and relative density is 0.52.
Q 32.
A bottle can hold 100 g of water at 4°C.What mass of sea water (density =
) can it hold ?
Q 33.
The mass of a block made of certain material is 13 5 kg and its volume is
float or sink in water ? Give a reason for your answer.
Q 34.
Calculate the pressure when a force of 200 N acts on an
Q 35.
State one important effect produced by the buoyant force exerted by water.
Q 36.
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 37.
Why do objects float or sink when placed on the surface of a liquid ?
Q 38.
Pascal’s law states that a fluid in a confined space expands into every possible space if it is put under pressure.This law plays a very important role in our lives.Give three applications with brief description.
Q 39.
Distinguish between speed and velocity.
Q 40.
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 41.
What is the SI unit of displacement ?
Q 42.
What do the graphs shown in Fig.indicate?
Q 43.
Using velocity time graph,establish the relation s = ut +
,where the symbols have their usual meanings.
Q 44.
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 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 racing car has a uniform acceleration of 4
.What distance will it cover in 10 s after start ?
Q 47.
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 48.
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 49.
In addition to speed,what else should be known to predict the position of a moving body from a given starting point ?
Q 50.
If velocity-time graph of a body is as shown in Fig.,what is the nature of motion ?
