A girl is riding her scooter and finds that its speedometer reading is constant. Class 9

A girl is riding her scooter and finds that its speedometer reading is constant. Class 9

Question 1.

A girl is riding her scooter and finds that its speedometer reading is constant. Is it possible for her scooter to be accelerating and if so, how? Class 9

Answer:

Yes, it is possible. Even if the speed is constant, the scooter can still be accelerating if there is a change in direction of motion. Acceleration depends on change in velocity, and velocity includes both speed and direction. So, when the scooter takes a turn or moves along a curved path, its direction changes, causing acceleration even though the speed remains constant. Example: A scooter moving at constant speed on a circular road is accelerating due to continuous change in direction.

Question 2.

A car starts from rest and its velocity reaches 24 m s^-1 in 6 s. Find the average acceleration and the distance travelled in these 6 s. Class 9

Answer:

Given:

1. Initial velocity, u = 0 m s^-1 (starts from rest)
2. Final velocity, v = 24 m s^-1
3. Time, t = 6 s

Finding average acceleration:

a = (v - u) /1 = (24 - 0) / 6 = 24 / 6 = 4 m s^-2 Finding distance travelled:

Using s = ut + 14 at²:

s = (0)(6) + 1/2 × 4 × (6)²

s = 0 + 1/2 × 4 × 36

s = 2 × 36 = 72 m

Verification using v² = u² + 2as:

24² = 0² + 2 × 4 × s

576 = 8s

s = 576/8 = 72 m