1. Welcome Rocketeers! DQ: Complete “Measuring Motion” worksheet Today:
Correct “Measuring Motion” worksheet
More Free Body Diagrams
HW: Complete “Force and Motion Ideas” Handout

2. Measuring Motion (back of paper)
a = change in velocity
change in time
A car accelerates from a standstill to 60 m/s in 10 seconds. What is the acceleration?
A car accelerates from 25 km/hr to 55 km/hr in 30 seconds. What is its acceleration?
A train is accelerating at a rate of 2 m/s. If its initial velocity is 20 m/s, what is its velocity after 30 seconds?
A runner achieves a velocity of 11.1 m/s, 9 sec after he begins. What is his acceleration? What distance did he cover?
a = 60 m/s
10 s
= 6 m/s/s
a = 30 km/hr
30 s
= 1 km/hr/s
If the train starts at 20 m/s then 1 second later it will be going 22 m/s
So 2 m/s for 30 seconds will add 60 m/s to the initial velocity (20 m/s) for a total of 80 m/s.
a = 2 m/s so for every second of time, the velocity is 2 m/s faster.
a = 11.1 m/s
9 s
= m/s/s

3. What is the average speed at 20 seconds. v = d/t so v = 12m/20s = 0
What is the average speed at 20 seconds? v = d/t so v = 12m/20s = 0.6 m/s What is the average speed at 30 seconds? v = d/t so v = 20m/30s = 0.67 m/s (rounded) What is the acceleration between 20 and 30 seconds? a = change in velocity change in time a = from 0.6 to 0.67 = 0.07m/s 10 seconds 10 s so a = m/s/s

4. What is the average speed at 40 seconds. v = d/t so v = 30m/40s = 0
What is the average speed at 40 seconds? v = d/t so v = 30m/40s = 0.75 m/s What is the average speed at 60 seconds? v = d/t so v = 56m/60s = 0.93 m/s (rounded) What is the acceleration between 20 and 30 seconds? a = change in velocity change in time a = from 0.75m/s to 0.93 m/s = 0.18 m/s 20 seconds 20 s so a = m/s/s

5. More Free Body Diagrams
Which of these diagrams show balanced forces?
Which show unbalanced forces?
Which diagrams show forces that would result in the object moving?
Which direction would they be moving?

6. Net Force These diagrams show unbalanced forces
The amount of the force on an object that is not balanced by an opposite force is called the net force
Net force can be thought of as the force left over when all the forces are added together – but be careful! If the forces are opposite, they are subtractive