Question:
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.
Answer:
(a) velocity is a function of time
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.
Why is it easier to swim in sea water than in river water ?
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 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 8.
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 9.
Why does a person feel pain when he stands on a pile of gravel than when he stands on a bed of sand ?
Q 10.
A body starts from rest.What is zero ?
Q 11.
What is represented by the graphs in Fig.?
.
Q 12.
Under what conditions(s) is the magnitude of average
Q 13.
Distinguish between speed and velocity.
Q 14.
What are the values of distance travelled and displacement in covering 10 m from P to Q and coming back ?
Q 15.
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 16.
Can displacement and distance ever be equal ?
Q 17.
In addition to speed,what else should be known to predict the position of a moving body from a given starting point ?
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.
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 20.
Relative density of silver is 10.8.The density of water is
.What is the density of silver in SI units ?
Q 21.
What does the odometer of an automobile measure?
Q 22.
What does the path of an object look like when it is in uniform motion?
Q 23.
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 24.
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 25.
Write the three equations of uniformly accelerated motion. Give the meaning of each symbol in them.
Q 26.
The density of turpentine oil is
.What will be its relative density ?
Q 27.
Why are sleepers used below the rails ?
Q 28.
A body thrown vertically upwards reaches a maximum height h.It then returns to ground.Calculate the distance travelled and the displacement.
Q 29.
What can you say about the motion of an object whose distance-time graph is a straight line parallel to the time axis ?
Q 30.
A particle moves over three quarters of a circle of radius r.What is the magnitude of its displacement ?
Q 31.
Use graphical method to derive the relation
-
= 2 as,where the symbols have their usual meanings.
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.
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 34.
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 35.
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 36.
A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.
Q 37.
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 38.
What will be the initial velocity of an object under free fall?
Q 39.
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 40.
Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.
Q 41.
An electric train is moving with a velocity of 120 km/h. How much distance will it move in 30 s ?
Q 42.
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 43.
Is distance a vector quantity ?
Q 44.
Name the terms represented by various symbols in the equation, v = u + at.
Q 45.
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 46.
Why is a slight blow on a cork of bottle fully filled with a liquid sufficient to break the bottle ?
Q 47.
What is thrust ?How is it related to pressure ? Give their units.
Q 48.
What is meant by buoyant force ? Describe an experiment to demonstrate the existence of this force.
Q 49.
An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.
Q 50.
Are motion and rest absolute or relative? Explain with an example.
