Olympiad Test: Motion And Time - Class 7 MCQ

When a body moves in a circle and returns to its starting point, the displacement is as follows:

• The initial position is point A.
• After completing the circle, the body returns to point A.
• Displacement is defined as the shortest distance between the initial and final positions.
• Since the body starts and ends at the same point, the displacement is zero.

The CGS unit of speed is centimetres per second (cm/s).

• The CGS (Centimetre-Gram-Second) system is a metric system for measuring.
• In this system, speed is expressed as distance over time.
• Thus, the appropriate unit for speed is cm/s, which indicates how many centimetres are travelled in one second.

Mean solar day = 24 h
= 24 × 60 × 60
= 86400 seconds 

In a constant speed the change in position of the body remains the same for a particular interval of time. Break time axis into small parts and see the distance travelled in each of these parts is the same in choices A, B and C (zero in ‘C’). But the distance changes in ‘D’. 

 Swinging pendulum is also under the influence  of gravitational force and is also changing its direction - hence it is not in uniform motion. It is non – uniform motion.
 

• The error is valid because the given question asks which of the listed options does not show oscillatory motion.
• A fan typically exhibits rotational motion, not oscillatory motion, as it rotates around a central axis.
• On the other hand, a swing, see-saw, and pendulum are classic examples of oscillatory motion, where they move back and forth in a regular cycle.
• Therefore, the correct answer should be "fan" and not "see-saw."

The fastest among the options is light.

• Light travels at approximately 299,792 kilometres per second in a vacuum.
• Wind speed can vary greatly but is generally much slower than light.
• Sound travels at about 343 metres per second in air, significantly slower than both wind and light.
• A cheetah can run at speeds up to 120 kilometres per hour, making it the fastest land animal, but still far slower than light.

An odometer measures distances travelled, not odour.

Distance travelled equals displacement when:

• The object moves in a straight line in a forward direction.

• The object changes directions frequently, as this increases distance.

• The object follows a complex path between two points.

• Distance and displacement are never equal under specific conditions.

The area of the shaded portion in the graph represents:

• The shaded area typically indicates distance.
• In a graph of speed against time, the area under the curve represents how far an object has travelled.
• This is because distance is calculated as speed multiplied by time.

The time taken by P is the lowest among the four, because more is the area under the wine, greater is the speed. Hence, P is the fastest. 

A light year is the distance covered by light in one year, so it is the unit of distance and not of time. 

Speed is the change of position of the body with respect to time. From the graph It increases and then becomes constant but not zero