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Q1. Average speed is a:
Average speed is a scalar quantity because it only has magnitude and no direction. It is calculated by dividing the total distance traveled by the total time taken, without any consideration of the direction of motion.
Q2. Numerical value of average speed for 32 m in 6 s is:
Average speed is calculated as total distance divided by total time. Here, distance is 32 m and time is 6 s. So average speed = 32 ÷ 6 = 5.33 m/s (approximately).
Q3. Speed and velocity have:
Both speed and velocity are measured in the same units, which are metres per second (m/s) in the SI system. The difference between them is that speed is a scalar quantity while velocity is a vector quantity that includes direction.
Q4. What quantity specifies both the speed and direction of an object’s motion?
Velocity is a vector quantity that specifies both the speed (magnitude) and the direction of an object’s motion. It provides more complete information about the motion than speed alone.
Q5. What is the formula for speed if distance is s and time is t?
Speed is defined as the distance traveled per unit of time. Therefore, the formula for speed is v = s/t, where s is the distance and t is the time taken.
Q6. How is the average speed of an object calculated?
Average speed is calculated by dividing the total distance traveled by the total time taken for the journey. It gives the overall rate of motion over the entire path.
Q7. Which activity helps estimate distance using average walking speed?
If we know our average walking speed, we can estimate the distance by measuring the time taken to walk from one place to another. For example, if we know we walk at 4 km/h and it takes us 0.5 hours to reach the bus stop, we can estimate the distance.
Q8. If average walking speed is 4 km/h and time taken is 0.5 h, distance is:
Distance is calculated by multiplying speed by time. Here, speed is 4 km/h and time is 0.5 hours. Distance = 4 × 0.5 = 2 km.
Q9. An object travels 16 m in 4 s and another 16 m in 2 s. What is the total distance?
The total distance is the sum of all distances traveled. First part is 16 m and second part is another 16 m. Total distance = 16 + 16 = 32 m.
Q10. What is the symbol for the SI unit of speed?
The SI unit of speed is metres per second, which can be written as m/s or m s⁻¹. Both forms are correct. m/s² is the unit of acceleration, ms is milliseconds, and kph is kilometres per hour.
Q11. What is the SI unit of speed?
The SI (International System of Units) unit of speed is metres per second, written as m/s. While km/h and cm/s are also units of speed, the standard SI unit is m/s.
Q12. Arithmetic mean of u and v is used when velocity changes:
The arithmetic mean (u+v)/2 is used to calculate average velocity when the acceleration is uniform (constant). In such cases, the velocity changes at a uniform rate, so the average velocity is simply the average of initial and final velocities.
Q13. The formula v = s/t is used to calculate:
The formula v = s/t is the basic formula for speed, where v is speed, s is distance, and t is time. It gives the rate at which distance is covered.
Q14. In v_av = (u + v)/2, what does ‘v’ represent?
In the formula for average velocity v_av = (u + v)/2, the symbol ‘u’ represents the initial velocity and ‘v’ represents the final velocity. This formula is used when acceleration is uniform.
Q15. Kilometre per hour is written as:
Kilometre per hour can be written in different ways: km/h, km h⁻¹, or kmph. All are acceptable notations. km/h² would be the unit of acceleration, not speed.
Q16. Centimetre per second is written as:
Centimetre per second is written as cm/s or cm s⁻¹. cm/s² would be the unit of acceleration, not speed. cms without a slash is not a standard unit notation.
Q17. If a car travels 100 km in 2 hours, what is its average speed?
Average speed is distance divided by time. Distance = 100 km, time = 2 hours. Average speed = 100 ÷ 2 = 50 km/h.
Q18. The quantity that describes motion more completely than speed is:
Velocity describes motion more completely than speed because it includes both the speed and the direction of motion. Speed only tells us how fast an object is moving, while velocity tells us both how fast and in which direction.
Q19. Which statement about average speed is correct?
Average speed is correctly defined as the total distance traveled divided by the total time taken. It is a scalar quantity and is defined for both uniform and non-uniform motion. It is not always equal to instantaneous speed.
Q20. Velocity is defined as:
Velocity is defined as the speed of an object in a specified direction. It is a vector quantity that includes both magnitude (speed) and direction.
Q21. Average velocity equals average speed when motion is:
Average velocity equals average speed only when the motion is along a straight line without changing direction. In this case, the total distance traveled equals the displacement, so both quantities give the same numerical value.
Q22. The rate of motion in non-uniform motion is described by:
In non-uniform motion, the speed changes from moment to moment. The rate of motion at any particular instant is described by instantaneous velocity or instantaneous speed. Average speed gives the overall rate over the entire journey.
Q23. What is the rate at which an object moves called?
Speed is defined as the rate at which an object covers distance. It tells us how fast an object is moving. It is calculated as distance divided by time.
Q24. Which of these represents velocity?
Velocity is a vector quantity that includes both magnitude and direction. 20 m/s west gives both the speed (20 m/s) and the direction (west), so it represents velocity. 20 m/s is just speed.
Q25. Which equation represents average velocity for uniform acceleration?
For uniform acceleration, the average velocity is the arithmetic mean of the initial velocity (u) and final velocity (v). So v_av = (u + v)/2 is the correct equation.
Q26. For the object in Q20, what is the total time taken?
The object travels 16 m in 4 s and another 16 m in 2 s. So the total time taken is 4 s + 2 s = 6 s. (Reference to question Q9 in this set)
Q27. To specify the speed of an object, what do we require?
Speed is a scalar quantity, so we only need its magnitude (numerical value) to specify it. We do not need direction to specify speed. Direction is only needed for velocity.
Q28. The speed of an object:
The speed of an object need not be constant. It can change over time, which is called non-uniform motion. In many real-life situations, objects move with varying speeds.
Q29. The primary difference between speed and velocity is:
The primary difference between speed and velocity is that speed does not include direction (scalar), while velocity includes direction (vector). Both are calculated using similar methods and have the same units.
Q30. How is the speed of an object defined?
Speed is defined as the distance traveled by an object per unit of time. It is the rate at which distance is covered. Displacement per unit time would be velocity.
Q31. How can the velocity of an object be changed?
Velocity is a vector quantity that includes both speed and direction. Therefore, velocity can change if the speed changes, if the direction changes, or if both change simultaneously.
Q32. Which of these represents speed?
Speed is a scalar quantity that only has magnitude. 5 m/s gives only the magnitude (5 metres per second), so it represents speed. 5 m/s² is acceleration. 10 m/s east and 10 km/h north include direction, so they represent velocity.
Q33. If equal distances are covered in equal intervals of time, speed is:
When an object covers equal distances in equal intervals of time, it is said to be moving with uniform speed. This is the definition of uniform motion.
Q34. According to the text, objects are in non-uniform motion:
In real life, most objects are in non-uniform motion because their speed changes due to various factors like friction, traffic, or changing forces. Perfect uniform motion is an idealization.
Q35. For uniform velocity:
Uniform velocity means that both the speed and direction of the object are constant. This means the object moves in a straight line with constant speed. If direction changes, velocity is not uniform.
Q36. Which of these is NOT a unit of speed?
Speed is measured as distance divided by time (m/s, km/h, cm/s). s/m is the reciprocal of speed and is not a unit of speed. It would be the unit of something like time per unit distance.
Q37. An object travels 32 m in 6 s. What is its average speed?
Average speed is calculated as total distance divided by total time. Distance = 32 m, time = 6 s. Average speed = 32 ÷ 6 = 5.33 m/s.
Q38. The symbol v_av stands for:
The symbol v_av stands for average velocity. It represents the average rate of change of position over a time interval. Sometimes it can also represent average speed, but in standard notation, v_av typically means average velocity.
Q39. The example (16 m + 16 m in 4 s + 2 s) demonstrates:
This example shows how to calculate average speed when an object covers different distances in different time intervals. The total distance is divided by the total time to get the average speed over the entire journey.
Q40. When an object moves along a straight line at variable speed, its rate of motion is expressed as:
When an object moves with variable speed, the speed at any particular instant is called instantaneous speed. Average speed gives the overall rate, while instantaneous speed tells us the exact speed at a specific moment.
Q41. What are the units of velocity?
Velocity is measured in units of distance per unit time. The SI unit of velocity is metres per second (m/s). m/s² is the unit of acceleration, m is the unit of distance, and s is the unit of time.
Q42. How is average velocity calculated for uniformly changing velocity?
For uniformly changing velocity (constant acceleration), the average velocity is the arithmetic mean of the initial velocity (u) and final velocity (v). So average velocity = (u + v)/2.
Q43. In most cases, the motion of objects is:
In real life, most objects move with non-uniform motion because their speed changes due to various factors like friction, air resistance, traffic, or changing forces. Perfect uniform motion is only an idealization.
Q44. Velocity of 5 m/s north gives information about:
The statement “5 m/s north” gives both the speed (5 m/s) and the direction (north). Therefore, it provides complete information about the velocity of the object.
Q45. A car travelling at an average speed of 50 km/h:
Average speed is the total distance divided by total time. A car with an average speed of 50 km/h may travel at speeds faster or slower than 50 km/h during different parts of the journey. The average just gives the overall rate.
Q46. In v_av = (u + v)/2, what does ‘u’ represent?
In the formula v_av = (u + v)/2, ‘u’ represents the initial velocity of the object at the start of the time interval. ‘v’ represents the final velocity at the end of the interval.
Q47. Speed of 5 m/s gives information about:
Speed of 5 m/s gives the magnitude of how fast the object is moving (5 metres per second). It does not give direction, and it is not acceleration or complete velocity information.
Q48. What term describes the distance travelled by an object in unit time?
Speed is defined as the distance traveled by an object in unit time. It tells us how much distance the object covers in one second (or one hour, etc.). Velocity is displacement in unit time, which includes direction.