Question:
What is the average velocity over the “round trip” of an object that is thrown straight up from the ground and falls straight back down to the ground?
Answer:
: Total displacement in this case ("round trip") = 0m
Let us assume time taken = T secs.
Average velocity (v) = Total Displacement ÷ Time Taken = 0 ÷ T = 0 m/sec
Note: In the above question, there are two important words "round trip" and "average velocity".
While solving numericals, focus on such words. These two words help in understand we need to compute displacement not distance. If average speed is being asked, we need to compute distance traveled.
Motion
Q 1.
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 2.
Derive graphically the equation of motion for position-velocity relation of a body moving with uniform acceleration.
Q 3.
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 4.
Are motion and rest absolute or relative? Explain with an example.
Q 5.
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 6.
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 7.
The density of turpentine oil is
.What will be its relative density ?
Q 8.
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 9.
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 10.
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 11.
If velocity-time graph of a body is as shown in Fig.,what is the nature of motion ?
Q 12.
Define thrust What is its unit ?
Q 13.
Distinguish between speed and velocity.
Q 14.
A particle is moving in a circle of diameter 5 m. Calculate the distance covered and the displacement when it completes 3 revolutions.
Q 15.
What can you calculate from speed-time graph of a body ?
Q 16.
What is represented by the graphs in Fig.?
.
Q 17.
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 18.
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 19.
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 20.
Can distance be negative ?
Q 21.
Use graphical method to derive the relation
-
= 2 as,where the symbols have their usual meanings.
Q 22.
When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Q 23.
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 24.
Fill in the blanks :
If the position of an object does not change with time, it is said to be at _____.
Q 25.
A body thrown vertically upwards reaches a maximum height h.It then returns to ground.Calculate the distance travelled and the displacement.
Q 26.
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 27.
Under what conditions(s) is the magnitude of average
Q 28.
What remains constant in uniform circular motion ?
Q 29.
Draw distance-time graph for a body (i) at rest (ii) in uniform motion (iii) in non-uniform motion.Discuss their interpretation.
Q 30.
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 31.
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 32.
Why is a slight blow on a cork of bottle fully filled with a liquid sufficient to break the bottle ?
Q 33.
Why does a person feel pain when he stands on a pile of gravel than when he stands on a bed of sand ?
Q 34.
What does the slope of distance-time graph indicate?
Q 35.
Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.
Q 36.
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 37.
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 38.
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 39.
A racing car has a uniform acceleration of 4
.What distance will it cover in 10 s after start ?
Q 40.
The displacement of a moving object in a given interval of time is zero.Would the distance travelled by the object also be zero ?Justify your answer.
Q 41.
Name the terms represented by various symbols in the equation, v = u + at.
Q 42.
Explain the terms : uniform motion and non-uniform motion with examples.
Q 43.
Derive graphically the equation v=u + at,where the symbols have their usual meanings.
Q 44.
A stone tied to one end of a string is rotated in a circle.Explain what happens when the stone is released.
Q 45.
State velocity-time relation in uniformly accelerated motion. Use graphical method to obtain this relation.
Q 46.
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 47.
Relative density of silver is 10.8.The density of water is
.What is the density of silver in SI units ?
Q 48.
A metallic sphere of radius 2.0 cm is completely dipped in water.Find the force of buoyancy on it.
Q 49.
State one important effect produced by the buoyant force exerted by water.
Q 50.
What is the relationship between the buoyant force on an object and the liquid displaced by it ?
