Class 7 Science Chapter 9 MCQ

The movement of an objects is called motion, not be “stationary-motion”.

Here, all the statements are correct. Hence, your answer will be option [D].

As we know that, Speed = Distance/Time = 54 x 1000/90 x 60 =10 m/s

Here, all the statements are correct. Hence, your answer will be option [D].

The correct relationship is: S = 1 x D/ T Because, Speed = Distance travelled (D) / Time taken (T)

Here, all the statements are correct. Hence, your answer will be option [D].

Time taken for 20 oscillation = 32 s So, Time taken for 1 oscillation = 32 s / 20 = 1.6 s Thus, the time period of this pendulum is 1.6 seconds.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Explanation: Here the speed has given to us in the units of meters per second and we have to convert it into the units of kilometers per hour. In order to this, we have to convert 10 meters into kilometers by dividing it by 1000. Since there are 60 x 60 seconds in 1 hour. We have also 10 by 60 x 60. We can convert the speed of 10 meter per second into kilometers per hour by dividing the speed of 10 by 1000 and multiplying it by 60 into 60. Now, Speed = 10 meter / seconds = 10 x 60 x 60 / 1000 = 36 km/h Thus, a speed of 10 m/s is equal to 36 km/h

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Blinking of eyes is not a periodic phenomenon (i.e., it does not repeat after definite intervals of time), so we cannot measure the time using this phenomenon.

We know that, 1 kilometer = 1000 meter 320 km = 320000 meters 1 hour = 3600 seconds (60 x 60) Now, Speed = Distance travelled / Time taken = 320000 meter / 3600 = 3200/36 = 88.8 m/s

Different units of time are used depending on the need. For example, it is convenient to express your age in years rather than in days or hours. Rockets, launching satellites into earth’s orbit, often attain speeds up to 8 km/s. On the other hand, all units (given in options) are not suitable for expressing the speed of a rocket. Hence, your answer will be option [B].

We should first convert the time of 15 minutes into hours by dividing it by 60 = 15 /60 hours = 0.25 hour i)In the 1st case: Distance travelled = Speed x time = 40 x 0.25 km = 10 km ii)In the 2nd case: Distance travelled = Speed x time = 60 x 0.25 km = 15 km Total distance: 10 km +15 km = 25 km

The option [B] is not relevant to unit of speed. Rest of all could be the unit of speed, where necessary. Hence, your answer will be option [B].

The time measured by “Quartz clocks and watches” is much more accurate than that measured by clocks and watches which were available earlier. Thus, very accurate measurement of time is not possible by using “Quartz clocks and watches”. Quartz is a hard mineral consisting of silica. These days, the regular of oscillations or vibrations of a tiny quartz crystals when joined into an electric circuit, are used for measuring time very accurately.

The two extremely small units of time which are used for expressing very, very small-time intervals are “microsecond” and “nanosecond”. One microsecond is one-millionth of a second. A nanosecond is one-billionth of a second.

The distance time graph for an object which stops moving is a straight line parallel to the time axis. When an object becomes stationary its speed is zero. So, a straight-line graph parallel to the time-axis shows that the speed of object is zero. Thus, a straight-line graph parallel to the time axis or a horizontal line graph tells us that the object has become stationary or it is not moving.

A bar graph is a diagram which shows information as bar or thin rectangles of different heights. In bar graph, the position and heights of the bars represent the values of the variable quantity about which information is given. This graph shows the object price increase with year, runs with over, selling market with respect to year. Bar graphs are frequently used in newspaper, magazines and TV to present various types of information in an interesting way. A bar graph is also known as a “histogram”.

We know that the fact that the time period of a given pendulum is constant was discovered by a scientist named “Galileo Galilei” just by chance. The periodic motion of a pendulum is utilized in pendulum clocks for measuring time. Remember, the pendulum clocks were big and bulky so they could not be carried everywhere is easily. In order to make small, light and portable clocks and watches a kind of modified pendulum was developed which is much smaller and compact than the traditional pendulum used in pendulum clocks, which is called balance wheel.

In order to solve this problem, we have to calculate the speed of both the trains separately. The train having higher speed will have travelled faster: We know that, Speed = Distance travelled / Time taken Distance travelled by train “A” = 150 km Time taken by train “A” = 3 h Speed of train “A” = 150 km / 3 h = 50 km/h Again, we know that: Speed = Distance travelled / Time taken Distance travelled by train “B” = 180 km Time taken by train “B” = 4 h Speed of train “B” = 180 km / 4 h = 45 km/h

We know that the distance time graph is also called “Line graphs”. This line graph shows the variation of distance travelled by a moving object with time. A line graph can also be drawn to show the variation of any other related quantities such as a variation of weight of a man with age. So, here option [C] is the correct answer.

Explanation: The formula for the calculating speed is: Speed = Distance travelled / Time taken Here, Distance travelled = 70 m Time taken = 20 s So, putting these values in the above formula, we get: Speed = 70 m / 20 s = 3.5 m/s Thus, the speed of scooter is 3.5 meter per second.