ACC facts & stats

Question 1

What is the SI unit of acceleration?

Accepted Answer

Meters per second squared (m/s²). Acceleration is change in velocity (m/s) per second, giving meters per second squared.

Question 2

About how fast do falling objects accelerate near Earth's surface, ignoring air?

Accepted Answer

9.8 m/s². Near Earth's surface, gravity accelerates falling objects at about 9.8 meters per second every second.

Question 3

With no air resistance, a heavy ball and a light ball dropped together will do what?

Accepted Answer

Hit the ground at the same time. In a vacuum all objects fall with the same acceleration, as shown with a hammer and feather on the Moon.

Question 4

Starting from rest, an object accelerates at 2 m/s² for 5 seconds. How fast is it going?

Accepted Answer

10 m/s. From rest, final speed equals acceleration times time: 2 m/s² x 5 s = 10 m/s.

Question 5

Acceleration that slows a moving object down is commonly called what?

Accepted Answer

Deceleration. Deceleration is the everyday name for acceleration that acts opposite to motion and reduces speed.

Question 6

Standard gravity (1 g) is defined as exactly how many m/s²?

Accepted Answer

9.80665. Standard gravity was defined as exactly 9.80665 m/s², a reference value used for g-force and weight.

Question 7

What is the formula for centripetal acceleration of an object in circular motion?

Accepted Answer

v²/r. An object moving at speed v on a circle of radius r accelerates toward the center at v squared over r.

The basics