Motion in one dimension intro

What is the rate of change in velocity known as?

Ram travels at a speed of 20 km/hr while going to school. While coming back, he travels at a speed of 30 km/hr(due to less traffic). What his it’s average speed?

• 25km/hr

• 26km/hr

• 20km/hr

• 24km/hr

• Cant be determined

Answer explanation

To find the average speed for the round trip, use the formula: Average Speed = 2xy / (x + y), where x = 20 km/hr and y = 30 km/hr. This gives: 2*20*30 / (20 + 30) = 1200 / 50 = 24 km/hr.

During which interval is the object traveling at a constant velocity?

• B to C

• D to E

• F to G

• it traveling at a constant velocity during all of the intervals shown.

Answer explanation

The object is traveling at a constant velocity during all intervals shown, indicating no changes in speed or direction. Therefore, the correct answer is that it is traveling at a constant velocity during all of the intervals.

Acceleration is

• increasing speed

• decreasing speed

• changing direction

• all of the above

Answer explanation

Acceleration refers to any change in velocity, which includes increasing speed, decreasing speed, or changing direction. Therefore, the correct answer is 'all of the above'.

A particle is moving in a circular path of radius r.

The displacement after half a circle would be:

• (a) Zero

• (b) πr

• (c) 2r

• (d) 2πr

Answer explanation

After half a circle, the particle moves from one side of the diameter to the opposite side. The straight-line distance (displacement) between these two points is equal to the diameter, which is 2r.

When a car driver travelling at a speed of 10 m/s applies brakes and brings the car to rest in 20 s, then the retardation will be:

• (a) + 2 m/s²

• (b) − 2 m/s²

• (c) − 0.5 m/s²

• (d) + 0.5 m/s²

Answer explanation

To find retardation, use the formula: retardation = (final velocity - initial velocity) / time. Here, final velocity = 0 m/s, initial velocity = 10 m/s, and time = 20 s. Thus, retardation = (0 - 10) / 20 = -0.5 m/s². The correct choice is (c) -0.5 m/s².

In which of the following cases of motions, the distance moved and the magnitude of the displacement are equal?

i. If the car is moving on a straight road

ii. If the car is moving in circular path

iii. The pendulum is moving to and fro

iv. The earth is moving around the sun

• (a) only(ii)

• (b) (i) and (iii)

• (c) (ii) and (iv)

• (d) only (i)

Answer explanation

The distance moved and the magnitude of the displacement are equal only when the motion is in a straight line without changing direction, as in case (i). In other cases, the path taken affects the displacement.

Question 1. A worker covers a distance of 40 km from his house to his place of work, and 10 km towards his house back. Then the displacement covered by the worker in the whole trip is

• (a) zero km

• (b) 10 km

• (c) 30 km

• (d) 50 km

Answer explanation

The worker travels 40 km to work and then 10 km back, resulting in a net displacement of 40 km - 10 km = 30 km. Thus, the correct answer is (c) 30 km.

Question 17.Four cars A, B, C and D are moving on a levelled, straight road. Their distance time graphs are shown in the figure below. Which of the following is the correct statement regarding the motion of these cars?

• Car A is faster than car D

• Car B is the slowest

• Car D is faster than car C

• Car C is the slowest

Answer explanation

Car B has the steepest slope in the distance-time graph, indicating it covers the least distance over time, making it the slowest car. The other statements about the speeds of cars A, C, and D are incorrect.

The speedometer of a car shows which of the following?

• Uniform speed

• Average Speed

• Instantaneous Speed

• Distance

• Non uniform speed

Answer explanation

The speedometer measures the car's speed at a specific moment, which is known as instantaneous speed. It does not provide information about average speed or distance traveled.