Question:
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?
Answer:
: You may compute arithmetic mean to compute average speed.
Alternately,
Total Time taken = 2t seconds
Total Distance covered = 3t + 5t = 8t m
Avg. Speed = Total Distance / Total Time = 8t/2t = 4m/s ... (answer)
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.
Are motion and rest absolute or relative? Explain with an example.
Q 4.
When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Q 5.
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 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.
Fill in the blanks :
If the position of an object does not change with time, it is said to be at _____.
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.
Fill in the blanks :
The rate of change of velocity of a moving body with time is called ______.
Q 10.
A body thrown vertically upwards reaches a maximum height h.It then returns to ground.Calculate the distance travelled and the displacement.
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 odometer of an automobile measure?
Q 13.
What does the path of an object look like when it is in uniform motion?
Q 14.
Under what conditions(s) is the magnitude of average
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.
Why are sleepers used below the rails ?
Q 18.
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 19.
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 20.
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 21.
What is meant by scalars and vectors?
Q 22.
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 23.
Can displacement and distance ever be equal ?
Q 24.
Explain the terms : uniform motion and non-uniform motion with examples.
Q 25.
Derive graphically the equation v=u + at,where the symbols have their usual meanings.
Q 26.
Use graphical method to derive the relation
-
= 2 as,where the symbols have their usual meanings.
Q 27.
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 28.
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 29.
Distinguish between speed and velocity.
Q 30.
What does the slope of distance-time graph indicate?
Q 31.
A scalar quantity has ?
(a) magnitude only
(b) direction only
(c) both direction and magnitude
(d) none of these
Q 32.
In addition to speed,what else should be known to predict the position of a moving body from a given starting point ?
Q 33.
A particle moves over three quarters of a circle of radius r.What is the magnitude of its displacement ?
Q 34.
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 35.
The density of turpentine oil is
.What will be its relative density ?
Q 36.
Why is it easier to swim in sea water than in river water ?
Q 37.
Why does a person feel pain when he stands on a pile of gravel than when he stands on a bed of sand ?
Q 38.
An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.
Q 39.
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 40.
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 41.
If velocity-time graph of a body is as shown in Fig.,what is the nature of motion ?
Q 42.
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 43.
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 44.
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 45.
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 46.
Name the quantity that represents rate of change of velocity ?
Q 47.
Draw distance-time graph for a body (i) at rest (ii) in uniform motion (iii) in non-uniform motion.Discuss their interpretation.
Q 48.
A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.
Q 49.
The speed-time graph for a car is shown is figure below.
(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 the period.
(b) Which part of the graph represents uniform motion of the car?
Q 50.
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 |
