WORK AND MOTION

Review part 2

Independent Variable

A variable that you can choose to change/manipulate

What you think affects an outcome Example:

You think that the length of a ramp will affect how much force you need to push a box up a ramp.

Independent Variable = length of ramp

Dependent Variable

Depends on Independent Variable (outcome)

You can not choose to change it directly Example:

As you increase the length of a ramp, the amount of force needed to push a box up it decreases.

Independent variable = length of rampDependent variable = amount of force

Control group

These are the variables in an experiment that do not change.

Example:In the potato lab, we used the same amount

of potato strips, both beakers had 250ml of tap water, and both beakers received the same amount of light.

Putting Data in Tables

Independent Variables

Length of ramp

Dependent Variables

Force

1m 5N

1.5m 6N

2m 7N

2.5m 8N

3m 9N

3.5m 10N

Graphing Data

1 2 3 40

5

10

15

20

25

30

Length affects amount of force

Length of Ramp in meters(Independent Variable)

Am

ou

nt

of

Fo

rce(

N)

(Dep

end

ent

Var

iab

le)

Work vs. No Work Alexis Reads a

Book No Work

Roy draws a picture of a car

Work

Krysta walks to the band hall

Work

Josh is trying to push a wall

No Work

Balanced Forces

Equal Forces acting in opposite directions on an object

No Movement!!!!

Think of the See-Saw!!!!!

Unbalanced Forces

Unequal Forces acting in opposite directions on an object

Causes MOTION!!!!

Think See-Saw!!!

Calculating Work

Work = Force x Distance W = F x d What is the unit for Force?

Newtons (N) What is the unit for distance?

Meters (m) What is the unit for work?

Joules (J)

Math Practice (Multiplying)25 x 0 =

25 x 2 =

25 x 0.3 =

25 x 2.5 =

32 x 11.1 =

12 x 2.15 =

1.83 x 5.6 =

3.56 x 10.01 =

Math Practice Answers

25 x 0 = 0

25 x 2 = 50

25 x 0.3 = 7.5

25 x 2.5 = 62.5

32 x 11.1 = 355.2

12 x 2.15 = 25.8

1.83 x 5.6 = 10.248

3.56 x 10.01 = 35.6356

Rally Coach

The partner to the left will do math problem 1 while the partner to the right watches and makes sure he/she is working the problems correctly.

1) 35 x 2.5 =

Answer is 87.5Switch partners

2) 16.15 x 12 =

Answer is 193.8

Work Problems

1. Sally uses 100N of force to push a box up a ramp a distance of 2.5m. Calculate the Work.

2. Mark applied 150N of force to kick a soccer ball a distance of 12m. Calculate the Work.

Work Problems

3. Amy used a 3.12m ramp to load the lawn mower on to the truck bed. If she had to use 50N of force to push the mower, how much work did she do?

Work Problems

4. Tom used 90N of force to throw a football a distance of 21m. Calculate the work

5. Mary used 35N of force to push the shopping cart a distance of 4.1m. Calculate the Work.

Work Problems

Jack and Jill are sitting on a see-saw. Jack is sitting 1.2m above the ground and exerting a force of 23N. Jill is sitting on the opposite end of the see-saw and is exerting a force of 23N. If she is sitting 1.2m above the ground, how much work is being done by Jack and Jill on the see-saw?