Question:
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 ?
Answer:
In Fig.,ABCD is a square field of side 10 m.
Time for one round = 40 s,
Total time = 2 min 20 s = (2 x 60 + 20) s = 140 s
Number of rounds completed = = 3.5
If farmer starts from A, he will complete 3 rounds (A→B → C→ D →A) at A.In the last 0.5 round starting from A, he will finish at C.
Displacement = AC,where AC =
=yJjO2 +102 = I0√2m
Motion
Q 1.
Derive graphically the equation of motion for position-velocity relation of a body moving with uniform acceleration.
Q 2.
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 3.
A particle moves over three quarters of a circle of radius r.What is the magnitude of its displacement ?
Q 4.
Write the three equations of uniformly accelerated motion. Give the meaning of each symbol in them.
Q 5.
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 6.
What is represented by the graphs in Fig.?
.
Q 7.
Why is a slight blow on a cork of bottle fully filled with a liquid sufficient to break the bottle ?
Q 8.
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 9.
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 10.
When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Q 11.
Under what conditions(s) is the magnitude of average
Q 12.
A body starts from rest.What is zero ?
Q 13.
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 14.
What will be the initial velocity of an object under free fall?
Q 15.
Name the quantity that represents rate of change of velocity ?
Q 16.
What conclusion do you draw when displacement-time graph of a body is as shown in Fig.?
Q 17.
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 18.
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 19.
What is pressure in case of fluids ? What is Pascal’s law ?
Q 20.
Why does a person feel pain when he stands on a pile of gravel than when he stands on a bed of sand ?
Q 21.
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 22.
What can you say about the motion of an object whose distance-time graph is a straight line parallel to the time axis ?
Q 23.
Draw speed-time graph for a body (i) at rest (ii) in uniform motion (iii) in uniformly accelerated motion.Discuss the results briefly.
Q 24.
A body thrown vertically upwards reaches a maximum height h.It then returns to ground.Calculate the distance travelled and the displacement.
Q 25.
What is the relationship between the buoyant force on an object and the liquid displaced by it ?
Q 26.
A body is moving uniformly with a velocity of 5 m/s. Find graphically the distance travelled by it in 5 s.
Q 27.
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 28.
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 29.
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 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.
Define buoyant force.What is its unit ?
Q 32.
The following is the distancc-time table of a moving car.
(a) Use a graph paper to plot the distance travelled by the car versus the time.
(b) When was the car travelling at the greatest speed ?
(c) What is the average speed of the car ?
(d) What is the speed between 11.25 am and 11-40 am ?
(e) During a part of the journey, the car was forced to slow down to 12 km/h.At what distance did this
| Time | Distance |
|---|
10.05 am
10.25 am
10.40 am
10.50 am
11.00 am
11.10 am
11.25 am
11.40 am | 0 km
5 km
12km
22 km
26 km
28 km
38 km
42 km |
Q 33.
Using velocity time graph,establish the relation s = ut +
,where the symbols have their usual meanings.
Q 34.
State velocity-time relation in uniformly accelerated motion. Use graphical method to obtain this relation.
Q 35.
A hydraulic automobile lift is designed to lift cars with a maximum mass of 3000 kg.The area of the piston carrying the load is
.What maximum pressure would the smaller piston have to bear ?
Q 36.
Relative density of silver is 10.8.The density of water is
.What is the density of silver in SI units ?
Q 37.
A body of 2.0 kg floats in a liquid.What is the buoyant force on the body ?
Q 38.
Define pressure.What is its unit ?
Q 39.
State one important effect produced by the buoyant force exerted by water.
Q 40.
The density of turpentine oil is
.What will be its relative density ?
Q 41.
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 42.
A body travels a distance of 15 m from A to B and then moves a distance of 20 m at right angles to AB.Calculate the total distance travelled and the displacement.
Q 43.
What is the acceleration of a body moving with uniform velocity ?
Q 44.
In addition to speed,what else should be known to predict the position of a moving body from a given starting point ?
Q 45.
What are the values of distance travelled and displacement in covering 10 m from P to Q and coming back ?
Q 46.
If velocity-time graph of a body is as shown in Fig.,what is the nature of motion ?
Q 47.
What do the graphs shown in Fig.indicate?
Q 48.
Explain the terms : uniform motion and non-uniform motion with examples.
Q 49.
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 50.
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 ?
