Question:
Define the term uniform acceleration.Give one example of uniformly accelerated motion.
Answer:
Refer to Art.1.7,Page 8.
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.
Are motion and rest absolute or relative? Explain with an example.
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.
A body thrown vertically upwards reaches a maximum height h.It then returns to ground.Calculate the distance travelled and the displacement.
Q 8.
Can displacement and distance ever be equal ?
Q 9.
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 10.
Why are sleepers used below the rails ?
Q 11.
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 12.
What does the path of an object look like when it is in uniform motion?
Q 13.
What does the slope of distance-time graph indicate?
Q 14.
Fill in the blanks :
If the position of an object does not change with time, it is said to be at _____.
Q 15.
Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.
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.
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 20.
Relative density of silver is 10.8.The density of water is
.What is the density of silver in SI units ?
Q 21.
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 22.
What is meant by scalars and vectors?
Q 23.
What does the odometer of an automobile measure?
Q 24.
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 25.
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 26.
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 27.
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 28.
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 29.
What is SI unit of speed ? Is it same for velocity ?
Q 30.
What is the acceleration of a body moving with uniform velocity ?
Q 31.
Draw distance-time graph for a body (i) at rest (ii) in uniform motion (iii) in non-uniform motion.Discuss their interpretation.
Q 32.
Draw speed-time graph for a body (i) at rest (ii) in uniform motion (iii) in uniformly accelerated motion.Discuss the results briefly.
Q 33.
Define buoyant force.What is its unit ?
Q 34.
What is the density of water at 4°C ?
Q 35.
State Archimedes’ Principle ? What is the relation between true weight,apparent weight and the buoyant force ?
Q 36.
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 37.
A particle is moving in a circle of diameter 5 m. Calculate the distance covered and the displacement when it completes 3 revolutions.
Q 38.
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 39.
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 40.
Under what conditions(s) is the magnitude of average
Q 41.
What remains constant in uniform circular motion ?
Q 42.
If velocity-time graph of a body is as shown in Fig.,what is the nature of motion ?
Q 43.
Explain the terms : uniform motion and non-uniform motion with examples.
Q 44.
Use graphical method to derive the relation
-
= 2 as,where the symbols have their usual meanings.
Q 45.
State velocity-time relation in uniformly accelerated motion. Use graphical method to obtain this relation.
Q 46.
A Physics teacher explains the concept of relative velocity to her students in class. She emphasises that when two bodies are moving in opposite directions, their relative velocity is sum of the velocities of the two. And when two bodies are moving in the same direction, their relative velocity is difference of the velocities of the two. Students are confused. The teacher then takes two balls one red and the other green. She says suppose red ball moves with a velocity of 5 m/s and green ball moves with a velocity of 4 m/s from a common point, and along the same straight line. If red ball is moving to the right and green ball is moving to the left, then after 1 sec, red ball is at R', where RR' = 5 m and green ball is at G' where GG' = 4 m, In Fig.(a).The distance between the two balls after 1 sec = G' R' = GG' + RR' = (4 + 5) = 9 m.
This is the magnitude of their relative velocity. If both the balls are moving to the right, as shown in Fig. (b), the distance between the two balls after 1 sec. = G' R' = RR' - GG' = 5 - 4 = 1 m.Read the above passage and answer the following questions :
(i) What value has the Physics teacher displayed ?
(ii) What have the students picked up?
(iii) Give at least one practical example of the concept.
Q 47.
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 48.
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 49.
Calculate the mass of a body whose volume is
and relative density is 0.52.
Q 50.
A metallic sphere of radius 2.0 cm is completely dipped in water.Find the force of buoyancy on it.
