E. Solving Problems using the motion equations

 

Ex 3) Starting from rest, an object accelerates at a rate of 12 m/s2. What is the velocity of the object at the end of 3 seconds?

Problem Solving Steps

• Step 1 - Read for information
• Step 2 - List information
• Step 3 - Plug in and Solve

 

 

 

Ex 3) Starting from rest, an object accelerates at a rate of 12 m/s2. What is the velocity of the object at the end of 3 seconds?

 

Vi = 0 (Starting from rest)

a = 12 m/s2

Vf = ?

t = 3 seconds



a = (Vf - Vi)/t

12 m/s2 = (Vf - 0)/3 secs

(Cross Multiply and Solve)



Answer: Vf =36 m/s

Ex 4) An object at 100. m/s accelerates at a rate of 120. m/s2. What will the velocity of this object be after .10 seconds?

 

Underline Info

 

 

Ex 4) An object at 100. m/s accelerates at a rate of 120. m/s2. What will the velocity of this object be after .100 seconds?

 

a = (Vf - Vi)/t

120. m/s2  = (Vf - 100. m/s)/.100 s

 

• Cross Multiply
• Answer : Vf = 112 m/s

 


3 ways to have non-zero acceleration

 

 

(to change velocity):

 

• Speed up

• Slow down

 

• Change Direction

 

F. Motion Terms and Direction

 

A whole branch of mathematics is required to deal with numbers that have direction

 

Trigonometry


This is why it is important to know which motion information has direction

 

Vector - a quantity that includes magnitude (a number) & direction

 

ex) displacement, acceleration, velocity

 

 

Scalar - a quantity that includes magnitude (a number) only

 

ex. time, distance, speed