A bus increases its speed from 36 km h to 72 km h in 10 seconds. What is its acceleration?

We know from the question that, Initial velocity of the bus, u = 36 km h = 36 × 5 18 = 10 m s . Final velocity of the bus, v = 72 km h = 72 × 5 18 = 20 m s . Time taken by the bus, t = 10 s . From the definition, We know that acceleration is the rate of change of velocity. ∴ a = v - u t ⇒ a = 20 - 10 10 = 1 m s 2

A scooter acquires a velocity of 36 km h in 5 s just after the start. Calculate the acceleration of the scooter.

We know from the question that, Initial velocity of the scooter, u = 0 Final velocity of the scooter, v = 36 km h = 36 × 5 18 = 10 m s . Time taken by the scooter, t = 5 s . From the definition of acceleration, we know that it is the rate of change of velocity. ∴ a = v - u t ⇒ a = 10 - 0 5 ⇒ a = 2 s

A bus travelling at 30 km h speeds up to 60 km h in 6 seconds. What is its acceleration in m s 2 ?

We know from the question that, Initial velocity of the bus, u = 30 km h = 30 × 5 18 = 50 6 m s Final velocity of the bus, v = 60 km h = 60 × 5 18 = 100 6 m s Time taken by the bus, t = 6 s From the definition, acceleration is the rate of change of velocity. ∴ a = v - u t ⇒ a = 100 6 - 50 6 6 ⇒ a = 50 36 = 1 . 389 m s 2

Describe the motion of a body which is accelerating at a constant rate of 10 m s 2 . If the body starts from rest, how much distance will it cover in 2 s.

We know from the question, Initial velocity of the body, u = 0 Acceleration of the body, a = 10 m s 2 Time taken by the body to cover the distance required, t = 2 s Considering the variables given, we can safely say that this uniformly accelerated motion. This is because the acceleration of the body is constant. To find the distance, we use the second equation of motion. s = u t + 1 2 a t 2 Substituting the values in this equation, we get, ∴ s = 0 × 2 + 0 . 5 × 10 × 4 ⇒ s = 20 m

E M B I B E

Essentials of PHYSICS Class IX>Chapter 1 - Motion>Practice Problems>Q 9

EASY

9th CBSE

IMPORTANT

Earn 100

A train starting from stationary position and moving with uniform acceleration attains a speed of $36 \frac{km}{h}$ in $10 minutes$ . Find its acceleration.

Important Questions on Motion

EASY

9th CBSE

IMPORTANT

Essentials of PHYSICS Class IX>Chapter 1 - Motion>Practice Problems>Q 10

A bus increases its speed from

36 \frac{km}{h}

to

72 \frac{km}{h}

in

10

seconds. What is its acceleration?

EASY

9th CBSE

IMPORTANT

Essentials of PHYSICS Class IX>Chapter 1 - Motion>Practice Problems>Q 11

A scooter acquires a velocity of

36 \frac{km}{h}

in

5 s

just after the start. Calculate the acceleration of the scooter.

EASY

9th CBSE

IMPORTANT

Essentials of PHYSICS Class IX>Chapter 1 - Motion>Practice Problems>Q 12

A bus travelling at

30 \frac{km}{h}

speeds up to

60 \frac{km}{h}

in

6

seconds. What is its acceleration in

\frac{m}{s^{2}}

?

EASY

9th CBSE

IMPORTANT

Essentials of PHYSICS Class IX>Chapter 1 - Motion>Practice Problems>Q 13

Describe the motion of a body which is accelerating at a constant rate of

10 \frac{m}{s^{2}}

. If the body starts from rest, how much distance will it cover in

2

s.

EASY

9th CBSE

IMPORTANT

Essentials of PHYSICS Class IX>Chapter 1 - Motion>Practice Problems>Q 14

Find the initial velocity of a car which is stopped in

10

seconds by applying brakes. The retardation due to brakes is

2.5 \frac{m}{s^{2}}

.

MEDIUM

9th CBSE

IMPORTANT

Essentials of PHYSICS Class IX>Chapter 1 - Motion>Practice Problems>Q 15

A body starting from rest travels with uniform acceleration. If it travels

100 m

in

5 s

, what is the value of the acceleration?

EASY

9th CBSE

IMPORTANT

Essentials of PHYSICS Class IX>Chapter 1 - Motion>Assignment>Q 1

"The direction in which an object moves is given by the direction of the velocity of the object and not by the direction of the acceleration". Give an example to justify that.

EASY

9th CBSE

IMPORTANT

Essentials of PHYSICS Class IX>Chapter 1 - Motion>Assignment>Q 2

Define acceleration of a body.