Question

q1
a ball is rolled at a speed of 12 m/s. after 3 seconds it comes to a stop. what is the acceleration of the ball?
a. -3 m/s²
b. 3 m/s²
c. 0.33 m/s²
d. -0.33 m/s²
q2
a parachute slows a skydiver from 85 m/s to 45 m/s in 4.5 seconds? what is the acceleration of the parachute?
a. 8.9 m/s²
b. -8.9 m/s²
c. 0.1 m/s²
d. -0.1 m/s²
q3
a plane taking off from the runway. this is an example of
a. speed
b. velocity
c. acceleration
d. all of the above
q4
the fastest pitch ever thrown was 169.14 kph (105.1 mph). this is an example of
a. speed
b. velocity
c. acceleration
d. none of the above

Explanation:

Q1

Step1: Recall the acceleration formula

The formula for acceleration is \(a=\frac{v - u}{t}\), where \(v\) is the final velocity, \(u\) is the initial velocity, and \(t\) is the time.

Step2: Identify the values

Here, \(u = 12\ m/s\), \(v=0\ m/s\) (comes to a stop), and \(t = 4\ s\).

Step3: Substitute into the formula

\(a=\frac{0 - 12}{4}=\frac{- 12}{4}=-3\ m/s^{2}\)

Q2

Step1: Recall the acceleration formula

The formula for acceleration is \(a=\frac{v - u}{t}\), where \(v\) is the final velocity, \(u\) is the initial velocity, and \(t\) is the time.

Step2: Identify the values

Here, \(u = 85\ m/s\), \(v = 45\ m/s\), and \(t=4.5\ s\).

Step3: Substitute into the formula

\(a=\frac{45 - 85}{4.5}=\frac{-40}{4.5}\approx - 8.9\ m/s^{2}\)

Q3

Step1: Understand the concepts

• Speed: Magnitude of rate of motion.
• Velocity: Speed with direction.
• Acceleration: Rate of change of velocity.
• When a plane takes off, its velocity is changing (increasing), so it is an example of acceleration.

Q4

Step1: Understand the concepts

• Speed: Magnitude of rate of motion.
• Velocity: Speed with direction.
• Acceleration: Rate of change of velocity.
• The fastest pitch is given as a magnitude (\(169.14\ kph\)), so it is an example of speed.

Answer:

Q1: A. \(-3\ m/s^{2}\)
Q2: B. \(-8.9\ m/s^{2}\)
Q3: C. Acceleration
Q4: A. Speed