Archives

Plot a distance-time graph of the tip of the second hand of a clock by selecting 4 points on x-axis and y-axis respectively. The circumference of the circle traced by the second hand is 64 cm.

Answer: We take four points on a clock at 3, 6, 9, and 12 hours before drawing the graph. At Point A the second-hand covers 16 cm and takes 15... View Article

Starting from A, Paheli moves along a rectangular path ABCD as shown in Figure. She takes 2 minutes to travel each side. Plot a distance-time graph and explain whether the motion is uniform or non-uniform.

Answer: Since the distance covered per unit time for the entire distance covered is not the same, the motion is non-uniform. A distance-time... View Article

A spaceship travels 36,000 km in one hour. Express its speed in km/s.

Answer: 10 km/s Spaceship speed = 36000 km/h In 1 hour spaceship travel = 36000 km We can say that in 60×60 second spaceship travel = 36000... View Article

The average age of children in Class VII is 12 years and 3 months. Express this age in seconds.

Answer: 12 years 3 months 12 years = 12 × 365 = 4380 3 months = 3 × 30 = 90 Adding together we get, 12 years 3 months = 4380 + 90 12 years 3... View Article

If Boojho covers a certain distance in one hour and Paheli covers the same distance in two hours, who travels in a higher speed?

Answer: Let the distance cover by Boojho be x km The speed of Boojho will be = (x/1) km/h Paheli also cover x km. Her speed will be = (x/2) km/h... View Article

Paheli and Boojho have to cover different distances to reach their school but they take the same time to reach the school. What can you say about their speed?

Answer: Because Paheli and Boojho arrive at school at the same time but travel a different distance, we can argue that their speeds are... View Article

A simple pendulum is oscillating between two points A and B as shown in Figure. Is the motion of the bob uniform or non-uniform?

Answer: A point mass attached to a light inextensible string and suspended from fixed support is called a simple pendulum. The vertical line... View Article

Boojho walks to his school which is at a distance of 3 km from his home in 30 minutes. On reaching he finds that the school is closed and comes back by bicycle with his friend and reaches home in 20 minutes. His average speed in km/h is (a) 8.3 (b) 7.2 (c) 5 (d) 3.6

Answer: (b) 7.2 Boojho home to school to again home From home to school distance is 3 km time taken is 30 min = (30/60) hour = 0.5 hour And in... View Article

The correct symbol to represent the speed of an object is (a) 5 m/s (b) 5 mp (c) 5 m/s-1 (d) 5 s/m

Answer: (a) 5 m/s Speed is defined as the rate of change of position of an object in any direction. Speed is measured as the ratio of distance... View Article

Fig shows an oscillating pendulum Time taken by the bob to move from A to C is t1 and from C to O is t2. The time period of this simple pendulum is (a) (t1 + t2 ) (b) 2 (t1 + t 2 ) (c) 3 (t1 + t 2 ) (d) 4 (t1 + t 2 )

Answer: (d) 4(t1 + t2) A point mass attached to a light inextensible string and suspended from fixed support is called a simple pendulum. The... View Article

Observe Figure. The time period of a simple pendulum is the time taken by it to travel from (a) A to B and back to A. (b) O to A, A to B and B to A. (c) B to A, A to B and B to O. (d) A to B.

Answer: (a) A to B and back to A. A point mass attached to a light inextensible string and suspended from fixed support is called a simple... View Article

If we denote speed by S, the distance by D and time by T, the relationship between these quantities is (a) S = D × T (b) T = S/D (c) S = 1/TxD (c) S = T/D

Answer: (c) S = 1/ T x D Speed is defined as the rate of change of position of an object in any direction. Speed is measured as the ratio of... View Article

A bus travels 54 km in 90 minutes. The speed of the bus is (a) 0.6 m/s (b) 10 m/s (c) 5.4 m/s (d) 3.6 m/s

Answer: (b) 10 m/s Given parameters Distance = 54 km Distance = 54 × 1000 m Distance = 54000m Time = 90 minitutes Time = 90 × 60 Time... View Article

Two students were asked to plot a distance-time graph for the motion described by Table A and Table B. The graph given in Figure is true for (a) both A and B. (b) A only. (c) B only. (d) neither A nor B.

Answer: (a) both A and B Since speed for A and B is constant, graph for A and B is a straight line as shown in the figure. A distance-time... View Article

Two clocks A and B are shown in Figure. Clock A has an hour and a minute hand, whereas clock B has an hour hand, minute hand as well as a second hand. Which of the following statement is correct for these clocks? (a) A time interval of 30 seconds can be measured by clock A. (b) A time interval of 30 seconds cannot be measured by clock B. (c) Time interval of 5 minutes can be measured by both A and B. (d) Time interval of 4 minutes 10 seconds can be measured by clock A.

Answer: (c) Time interval of 5 minutes can be measured by both A and B. Clock A doesn’t have a seconds hand. Hence seconds cannot be... View Article

Which of the following cannot be used for measurement of time? (a) A leaking tap. (b) Simple pendulum. (c) Shadow of an object during the day. (d) Blinking of eyes.

Answer: (d) Blinking of eyes. Blinking the eye is not a periodic phenomenon. Eyes do not blink at a fixed interval of time. Hence Blinking of... View Article

You are given three mirrors of different types. How will you identify each one of them?

Answer: We can identify the mirrors by forming images of an object which are given as below: In the case of a plane mirror, the image will... View Article

It was observed that when the distance between an object and a lens decreases, the size of the image increases. What is the nature of this lens? If you keep on decreasing the distance between the object and the lens, will you still able to obtain the image on the screen? Explain.

Answer: A convex lens is one that increases the size of the image as the distance between the object and the lens decreases which is a converging... View Article

Suppose we wish to obtain the real image of a distant tree. Explain two possible ways in which we can do it.

Answer: Two possible ways in which the real image of a distant tree can be obtained are given below : Concave mirror Convex lens We can use a... View Article

The distance between an object and a convex lens is changing. It is noticed that the size of the image formed on a screen is decreasing. Is the object moving in a direction towards the lens or away from it?

Answer: In a convex lens, if the size of the image obtained on a screen is decreasing on moving the object, then the object is moving in a path... View Article

M	T	W	T	F	S	S
		1	2	3	4	5
6	7	8	9	10	11	12
13	14	15	16	17	18	19
20	21	22	23	24	25	26
27	28	29	30