Kinematics Review

A quantity that is has magnitude and  direction is referred to as a

• vector quantity
• scalar quantity

Tags

NGSS.MS-PS2-2

NGSS.MS-PS2-4

NGSS.MS-PS2-5

You run from your house to a friend's house that is 3 km away. You then walk home. The distance you traveled is 6 km. What is your displacement? 

• 6  km
• 0 km

A hummingbird averages a speed of about 45 km/hour (Cool facts: They visit up to 1000 flowers per day, and reach maximum speed, while diving, up to 160 km/hour!). Ruby-throated hummingbirds take a non-stop trip across Gulf of Mexico in which they fly for 18 hours straight! How far is the trip across the Gulf of Mexico at their average speed?

• 810 km
• 2.5 km
• 3.6 km
• 360 km

A car is traveling south for 250 meters over the course of 100 seconds. What was the car's average velocity?

• 0.4 m/s south

• 0.4 m/s

• 2.5 m/s

• 2.5 m/s south

A car is travelling along the road. It starts at 10 m/s and accelerates to a velocity of 25 m/s. It speeds up over a period of 5 seconds. What is the acceleration?

Answer explanation

Our knowns are:

Vi = 10m/s; Vf = 25m/s; t = 5s

We are looking for acceleration (a)

Our formula is:

Vf = Vi + at

25m/s = 10m/s + a(5s)

-10m/s -10m/s

15 = a(5s)

divide both sides by 5s

t = 3m/s^2

A car is travelling along the road. It starts at 10 m/s and accelerates to a velocity of 25 m/s. It speeds up over a period of 5 seconds. What distance does it travel during this time?

• 62.5 m

• 77.5 m

• 82.5 m

• 87.5 m

Answer explanation

Our knowns are

Vi =10 m/s; Vf = 25 m/s; t = 5s

We are looking for distance. In order to find distance, we can first find acceleration.

Our formula is:

a = change in velocity/t

a = (25 m/s - 10 m/s)/5s

a = (15)/5

a = 3 m/s^2

Now distance:

d = vit + 1/2at^2

d = (10m/s)(5s) + (1/2)(3m/s^2)(5s)^2

d = 50 + 37.5

d = 87.5m

Tags

NGSS.MS-PS2-2

A bicyclist is travelling along a bike path in the park at a constant velocity of 4 m/s. A deer darts in front of the bicyclist and they hit the brakes. The brakes decelerate the bike at -2 m/s^2.

How long does it take the bicyclist to stop?

• 0.5s

• 1.0s

• 1.5s

• 2.0s

Answer explanation

Our knowns are:

Vi = 4 m/s, Vf = 0 m/s,

a = -2m/s^2

We are looking for time t

Our equation is

Vf = Vi + at

0 m/s = 4 m/s + -2m/s^2 (t)

add + 2 m/s^2 (t) to both sides

2 m/s^2(t) = 4 m/s

Divide both sides by 2 m/s^2

t = 2s

Tags

NGSS.MS-PS2-2

A _________ quantity is completely described by magnitude alone. A _________ quantity is
completely described by a magnitude with a direction.

• vector, scalar
• scalar, vector

An object is NOT accelerating if it is moving

• in a circle
• at constant velocity 
• at increasing speed
• only as influenced by gravity

A car slows down from +32 m/s to +8 m/s in 4 s. The acceleration is 

• 6 m/s/s opposite the motion
• 2m/s/s in the direction of motion
• 8 m/s/s opposite the motion

Tags

NGSS.MS-PS2-2