Linear Motion

Question 1

Which quantity is a vector?

Accepted Answer

Displacement — Displacement has magnitude and direction, so it is a vector.

Question 2

A car accelerates from rest at 3 m s⁻² for 5 s. Its final velocity is:

Accepted Answer

15 m s⁻¹ — v = u + at = 0 + 3 × 5 = 15 m s⁻¹.

Question 3

The SI unit of acceleration is:

Accepted Answer

m s⁻² — Acceleration is change of velocity per time, m s⁻².

Question 4

A body moving at constant velocity has an acceleration of:

Accepted Answer

Zero — Constant velocity means no change in velocity, so a = 0.

Question 5

A car travelling at 20 m s⁻¹ decelerates uniformly to rest in 4 s. Its deceleration is:

Accepted Answer

5 m s⁻² — a = (0 − 20) ÷ 4 = −5 m s⁻², a deceleration of 5 m s⁻².

Question 6

Using s = ut + ½at², an object starting from rest with a = 4 m s⁻² travels in 3 s a distance of:

Accepted Answer

18 m — s = 0 + ½ × 4 × 3² = ½ × 4 × 9 = 18 m.

Question 7

A stone with u = 10 m s⁻¹ accelerates at 2 m s⁻² over 24 m. Its final velocity using v² = u² + 2as is:

Accepted Answer

14 m s⁻¹ — v² = 10² + 2(2)(24) = 100 + 96 = 196, v = 14 m s⁻¹.

Question 8

Distance differs from displacement because distance:

Accepted Answer

Is the total path length — Distance is the scalar total path length; displacement is directed.

Question 9

A runner covers 100 m in 20 s. The average speed is:

Accepted Answer

5 m s⁻¹ — Speed = distance ÷ time = 100 ÷ 20 = 5 m s⁻¹.

Question 10

Which equation should be used when time is NOT given?

Accepted Answer

v² = u² + 2as — v² = u² + 2as contains no time term.