kinematics exam review

Paul Wallface has reached the end of a long hill and encounters a wall, thus he abruptly decelerates from 36.0 m/s to 0.0 m/s in .008 seconds. Determine Paul's acceleration rate

• 4500 m/s²

• -4500 m/s²

• .288 m/s²

• 0 m/s²

Answer explanation

using the velocity equation to solve for a.

vf = vi + at

a = vf-vi/t

thus, 0-36/.008 equals -4500 m/s²

Tags

NGSS.HS-PS2-1

1. Luigi is running for home base. He dives head first, hitting the ground at 6 m/s and reaching the base at 3 m/s, accelerating at -6 m/s². Determine the distance Luigi slides across the ground before touching the base.

• .50 m

• 0 m

• 2.3 m

• 3.3 m

Answer explanation

Using the timeless equation

vf² = vi² + 2ax solve for x

x = vf² - vi² /2a

x = 3^{2 -} 6² / 2(-6) = 2.25 or 2.3 m

Tags

NGSS.MS-PS2-2

1. The tallest building in the United States is the One World Trade Center in NYC. If a penny was dropped from the top of the 1776-foot (541.3 meter) tall tower onto your head, it would feel just like getting flicked in the head by someone’s finger.  During its free fall, the penny’s flat shape encounters so much air resistance that it’s final velocity is rather small.  Determine the time it takes the penny to hit your face at the bottom. (Remember that our calculations do not include air resistance.)

• 13.5 s

• 10.5 s

• 9.8 s

• 15 s

Answer explanation

Using the position equation:

x = vit + 1/2 at²

Vi = 0, so the equation becomes x = 1/2 at²

Then, solving for t

2x = at²

Then 2x/a = t²

Finally, t = √2x/a

t = √2(541.3)/9.8 = 10.5 s

Tags

NGSS.HS-PS2-1

According to the website zeroto60times, a 2012 Bugatti Veyron can acceleration from zero to 60 mph (26.8 m/s) in 2.4 s. How far does the car travel in those 2.4 s?

• 11.2 m

• 26.8 m

• 64.3 m

• 32.2 m

Answer explanation

use the displacement equation

X = (vf+vi/2)t

X = (26.8 + 0/2) 2.4 = 32.16 = 32.2 m

Tags

NGSS.HS-PS2-1

Which one of the following quantities is a change in velocity?

• distance

• displacement

• acceleration

• heat

A boat is initially moving at 20 m/s and accelerates at 2 m/s² for 10 s.  What is its final speed?    

• 30 m/s

• 20 m/s

• 40 m/s

• 50 m/s

Answer explanation

use the velocity equation

vf = vi + at

vf = 20 m/s + (2m/s²)(10 s) = 40 m/s

On Earth, what is the acceleration due to gravity?

• 9.8 m/s²

• depends on weight

• 1.4 m/s²

• 3 m/s²

A car drives in a straight line at a constant speed of 60 m/s for 5 seconds. Find its acceleration.

• 12 m/s²

• 300 m/s²

• 0 m/s²

• 5 m/s²

Answer explanation

acceleration is zero

A woman walks 10 blocks north. She then turns east and continues for another 15

blocks. How far away is she from her starting position and what direction is she

from that position?

• 18 blocks east of north

• 18 blocks, north of east

• 10 blocks, east
• 25 blocks, southeast

What are the components of a vector 9200 units, 22 degrees N of E?

• 8530 units east and 3446 units north

• 9500 units east and 4000 units north

• 0 units

• 3.847 units