Review: Newton’s First Law



Name: ____KEY___________________________ Date: _________________ Hr:_______

Unit 2 Review: Newton’s First Law

Complete this review packet to the best of your ability using your notes, labs, and previous worksheets. The amount of work you put into the review will reflect on your test. The review sheet covers the main topics of the test- you should still study your notes and other worksheets.

Define the following terms and provide examples of proper units for each:

Speed

the rate at which someone or something moves or travels

distance /time = Speed

Units: km/hr m/s mph

Velocity

Speed in a given directions; contains both a magnitude and a direction

Vector Quantity

Units: km/hr up m/s North mph down

Distance

the amount of space between two places or things

Units: cm m km inches miles

Displacement

the difference between the initial position of something and any later position; has magnitude and direction

Units: m up km south -miles

Force

something that causes a change in the motion of an object

Units: N

Define the following terms and provide examples of each:

Vector Quantity

are quantities that are fully described by both a magnitude and a direction

Equilibrium Rule

When all forces acting on an object are balanced; net force =0

Inertia

An object’s resistance to change what it is already doing.

Newton’s 1st Law

An object at rest will stay at rest and an object in motion will remain in motion unless acted upon by an outside force. A force is needed for an object to start moving, stop moving, or change direction. Also called the Law of Inertia.

Frame of Reference

something that is not moving with respect to an observer that can be used to detect motion

Motion

Change in position of an object with respect to time. 

Net force

the vector sum of all the forces that act upon an object.

Answer the questions below (you do NOT need to use complete sentences!)

1. What are 4 examples of everyday forces? What direction do these forces act?

Force Normal (Fn)- pushes an object up off a surface

Force of Gravity (Fg)- pulls an object down toward the center

Force of Friction (Ff)- in the opposite direction of the motion

Applied Force (Fa)- force given by another object pushing or pulling it. Direction is based on the direction the force is applied to an object.

2. What is the equation for speed? Time? Distance?

Speed = Distance/Time

Time=Distance/Speed

Distance= Speed * Time

3. Explain the statement: Velocity is to speed as displacement is to distance.

Velocity and Displacement are vector quantities and must have their nonvector component Speed or Distance to accurately describe the velocity or displacement. Velocities magnitude is describe by an objects speed and distance is the magnitude component of displacement.

4. If an object is in motion, how do you know if it is in equilibrium?

An object moving at a constant speed (velocity) will be in equilibrium

5. What are balanced forces? Unbalanced forces?

Balanced forces occur when an object is at rest or when moving at a constant velocity. The net force is equal to 0.

Unbalanced forces causes an object to start moving, stops movement, and causes a change in direction, acceleration and deceleration.

6. What symbol is used to represent vector quantities? What information can that symbol tell us?

The symbol is an Arrow. The length tells the magnitude and the tip of the arrow shows the direction.

7. On a distance-time graph, what does the magnitude (steepness) of the slope tell you?

How quickly an object is moving. A steep slope means it is moving quickly where a small slope shows and object is moving slow.

8. On a distance-time graph, what does the direction of the slope tell you?

The direction of the slope tells you whether the object is moving further away or closer to the starting position. The direction also shows the speed at which this is occurring.

9. Use Newton’s 1st law to explain why you lurch forward in a bus that suddenly slows and backward in a bus that is picking up speed.

Forward because your body want to continue moving forward at the same speed even though the bus slows down.

Backward because your body want to stay still or move at the slower speed.

10. If you toss a coin straight upward while riding in a train, where does the coin land (relative to your hand) when the motion of the train is along a straight line track? When the train slows while the coin is in the air? When the train turns right?

Straight up: Your hand

Slowing Train: In front of you

Turning Train(Right): To your left

11. If a person distributes their weight evenly among 2 scales, how would the reading of each scale compare to their original weight?

Each would show about ½ your weight.

Calculate: SHOW YOUR WORK (equation, plug in the numbers, and answer with units!)

1. A tennis ball travels the length of the court (24 m) in a total of 0.5 seconds. What is the average speed (m/s) of the ball?

24/.5= 48 m/s

2. The earth travels at a speed of 100,000 km/hr. How many min would it take the earth to travel 500 km?

500/100000= .005 hours

.005 hrs * 60 min = .3 minutes

3. How long will it take light moving at 300,000 km/s to reach us from the sun? The sun is 15,000,000 km from earth.

15000000/300000 = 50 s

4. The fastest train in the world moves at 500 km/hr. How far will it go in 45 min?

45 minutes= .75 hr

.75 X 500 = 375 km

Graphs: Construct 2 graphs using the data given below. Use your graphs to answer the questions for each data set.

|Distance (m) |Time (sec) |

|10 |20 |

|20 |40 |

|35 |70 |

|65 |130 |

|85 |170 |

|100 |200 |

1. Does this graph represent constant or changing speed? How do you know?

Constant Speed

The line is a diagonal line with a constant slope.

2. What is the average speed of the object?

100/200= .5 m/s

_______________________________________________________________________________

|Distance (m) |Time (sec) |

|15 |20 |

|25 |50 |

|40 |65 |

|70 |130 |

|90 |185 |

|100 |200 |

3. Does this graph represent constant or changing speed? How do you know?

Changing

The amount the time changes with each distance varies causing a line that’s slope changes.

4. Which section of the graph represents the highest speed? How do you know?

From 25-40 m

The steepest slope

5. What is the speed from time 130 to 185 s? What is the average speed of the object?

185s-130s=55s 90m-70m=20m 20m/55s=.36 m/s

100m / 200s= .5 m/s

6. On a distance time graph, how can you tell if an object is at rest?

Straight horizontal line that shows time changing but not distance.

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