Motion & Time - UPSC Sci Tech Free MCQ Test with solutions

• Speed is the measure of how quickly an object moves from one position to another. It is calculated as the distance traveled divided by the time taken to travel that distance.

 

Topic in NCERT: Speed

Line in NCERT: "The distance moved by an object in a unit time is called its speed."

Sundials utilize the position of the sun to cast a shadow, indicating the time, and are considered one of the first devices used to measure time, dating back to ancient Egypt. 

• Sand clocks: While ancient, sand clocks are not considered the earliest timekeeping devices. 
• Pendulum clocks: These were developed much later than sundials. 
• Stopwatches: Stopwatches are designed to measure specific time intervals, not the time of day, and came about even later than pendulum clocks. 

Topic in NCERT: Units of time and speed

Line in NCERT: "Sundials"

• The speedometer is a device found in vehicles that measures the current speed of the vehicle.
• It provides real-time information, allowing drivers to maintain safe speeds and abide by traffic regulations.
• Unlike an odometer, which measures distance traveled, the speedometer focuses solely on speed.
• Ammeter and voltmeter measure electrical current and voltage, respectively, and are not related to vehicle speed.

Topic in NCERT: Measuring Speed

Line in NCERT: "The speedometer records the speed directly in km/h."

The basic unit of distance is metre (m). The basic unit of time is second (s). Since we know that s=d/t. Therefore, the basic unit of speed is m/s.

So option D is the correct answer. 

Topic in NCERT: What you have Learnt

Line in NCERT: "The speed of an object is the distance travelled divided by the time taken to cover that distance. Its basic unit is metre per second (m/s)."

- A distance-time graph represents how distance changes with time.
- A straight line on a distance-time graph indicates a constant rate of change of distance over time.
- Uniform motion means an object travels equal distances in equal intervals of time.
- Therefore, for uniform motion, a distance-time graph is a straight line.
- Non-uniform motion, discontinuous motion, and accelerated motion would result in curves or discontinuities, not straight lines.

Topic in NCERT: Distance-Time Graph

Line in NCERT: "The distance-time graph for the motion of an object moving with a constant speed is a straight line."

 We know , 
1 km=1000m , 1 hour=3600s
1km/h=1000/3600m/s=5/18m/s
72km/h=72×5/18m/s
=4×5m/s
=20m/s.

Topic in NCERT:  Measuring Speed

Topic in NCERT: Speed

Oscillatory motion involves an object moving to and fro about a fixed point, such as the motion of a pendulum or the hands while running.

Topic in NCERT: Measuring of Time

Line in NCERT: "The to and fro motion of a simple pendulum is an example of a periodic or an oscillatory motion."

Time period = Total time taken/Number of oscillations
= 32s/20
=1.6 s
Time period = 1.6 s

Topic in NCERT: Measuring Time

Line in NCERT: "By dividing the time taken for 20 oscillations by 20, get the time taken for one oscillation, or the time period of the pendulum."