Practice Questions

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Practice — Velocity and acceleration • Acceleration

Acceleration from a change in speed

Difficulty: ★☆☆

1147

A car increases its speed from 4 m s^-1 to 10 m s^-1 in 3 s with constant acceleration. What is its acceleration?

Your Answer:

3 m s^-2

6 m s^-2

2 m s^-2

14 m s^-2

Solution:

Use \(a=\dfrac{v-u}{t}\).

Here \(u=4\), \(v=10\), \(t=3\).

So \(a=\dfrac{10-4}{3}=2\text{ m s}^{-2}\).

Acceleration from rest

Difficulty: ★☆☆

1148

A vehicle starts from rest and reaches 10 m s^-1 after 4 s at constant acceleration. Find the acceleration.

Your Answer:

10 m s^-2

4.0 m s^-2

0.4 m s^-2

2.5 m s^-2

Solution:

Since it starts from rest, \(u=0\).

Use \(a=\dfrac{v-u}{t}=\dfrac{10-0}{4}=2.5\text{ m s}^{-2}\).

Time to reach a given velocity

Difficulty: ★☆☆

1149

A car is moving at 3 m s^-1 and then accelerates at 6 m s^-2. How long does it take to reach 12 m s^-1?

Your Answer:

3 s

2 s

1.5 s

1 s

Solution:

Use \(v=u+at\).

So \(12=3+6t\).

Hence \(9=6t\), so \(t=1.5\text{ s}\).

Final velocity under constant acceleration

Difficulty: ★☆☆

1150

An aircraft is moving at 4 m s^-1 and accelerates at 3 m s^-2 for 5 s. What is its final velocity?

Your Answer:

7 m s^-1

11 m s^-1

19 m s^-1

15 m s^-1

Solution:

Use \(v=u+at\).

So \(v=4+3\times 5=19\text{ m s}^{-1}\).

Finding the initial velocity

Difficulty: ★☆☆

1151

A speedboat accelerates at 1.5 m s^-2 for 4 s and finishes with speed 9 m s^-1. What was its initial speed?

Your Answer:

2.5 m s^-1

3 m s^-1

15 m s^-1

6 m s^-1

Solution:

Use \(v=u+at\).

So \(9=u+1.5\times 4=u+6\).

Hence \(u=3\text{ m s}^{-1}\).