Question 3

What can you say about the motion of an object if its speed-time graph is a straight line parallel to the time axis?

Answer

The speed of the object is not changing with the time it means the object is in uniform motion. So , the object is moving with uniform motion.

- Q:-
Abdul, while driving to school, computes the average speed for his trip to be 20 km h

^{-1}. On his return trip along the same route, there is less traffic and the average speed is 40 km h^{-1}. What is the average speed for Abdul’s trip? - Q:-
Two objects, each of mass 1.5 kg, are moving in the same straight line but in opposite directions. The velocity of each object is 2.5 m s

^{-1}before the collision during which they stick together. What will be the velocity of the combined object after collision? - Q:-
How do poriferan animals differ from coelenterate animals?

- Q:-
Fig 8.11 shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:

*Fig. 8.11*(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:-
Two objects of masses 100 g and 200 g are moving along the same line and direction with velocities of 2 m s

^{-1}and 1 m s^{-1}, respectively. They collide and after the collision, the first object moves at a velocity of 1.67 m s^{-1}. Determine the velocity of the second object. - Q:-
Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?

- Q:-
The speed-time graph for a car is shown is Fig. 8.12.

*Fig. 8.12*(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:-
Why are we normally advised to take bland and nourishing food when we are sick?

- Q:-
An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down.

- Q:-
Why is the weight of an object on the moon 1/6th its weight on the earth?

- Q:-
An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down.

- Q:-
What happens to the force between two objects, if

(i) the mass of one object is doubled?

(ii) the distance between the objects is doubled and tripled?

(iii) the masses of both objects are doubled? - Q:-
During an experiment, a signal from a spaceship reached the ground station in five minutes. What was the distance of the spaceship from the ground station? The signal travels at the speed of light, that is, 3 × 10

^{8}m s^{-1}. - Q:-
Explain the basis for grouping organisms into five kingdoms.

- Q:-
A trolley, while going down an inclined plane, has an acceleration of 2 cm s

^{-2}. What will be its velocity 3 s after the start? - Q:-
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:-
The kinetic energy of an object of mass, m moving with a velocity of 5 m s

^{-1}is 25 J. What will be its kinetic energy when its velocity is doubled? What will be its kinetic energy when its velocity is increased three times? - Q:-
Fig 8.11 shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:

*Fig. 8.11*(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:-
In the hierarchy of classification, which grouping will have the smallest number of organisms with a maximum of characteristics in common and which will have the largest number of organisms?

- Q:-
A racing car has a uniform acceleration of 4 m s

^{-2}. What distance will it cover in 10 s after start?

- NCERT Chapter

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