Question

1. toby glances at the speedometer on his bicycle as he begins to roll downhill. it indicates he is traveling at 12 miles per hour when he initially looks at it and 20 miles per hour 4 seconds later. his acceleration is: a. 2 mph/sec. b. 3 mph/sec. c. 5 mph/sec. d. 8 mph/sec. 9. if an object is accelerated, all of the following may occur except: a. a change of speed. b. a change of direction. c. it remains motionless. d. a change of direction and speed.

Explanation:

Question 4

Step1: Calculate the change in speed

The formula for acceleration \(a=\frac{\Delta v}{\Delta t}\), where \(\Delta v = v_{final}-v_{initial}\). Here, \(v_{initial} = 12\) mph and \(v_{final}=20\) mph. So, \(\Delta v=20 - 12=8\) mph.

Step2: Calculate the acceleration

Given \(\Delta t = 4\) seconds. Using the formula \(a=\frac{\Delta v}{\Delta t}\), we substitute \(\Delta v = 8\) mph and \(\Delta t=4\) s. Then \(a=\frac{8}{4}=2\) mph/sec.

Acceleration is defined as a change in velocity. Velocity is a vector quantity (has both magnitude - speed and direction). If an object is accelerated, its velocity changes. A change in velocity can be a change in speed (magnitude of velocity), a change in direction (since velocity is a vector), or both. If an object remains motionless, its velocity is \(v = 0\) and there is no change in velocity (\(\Delta v=0\)), so it cannot be accelerating.

Answer:

a. 2 mph/sec.

Question 9