Physics Review

The Scientific Method Link the process of a police investigation of a car accident with the stages of the scientific method.

Link the process of a police investigation of a car accident with the stages of the scientific method.

Observation/collection Hypothesis Experiments/tests Interpret/revise hypothesis Conclusion

Observation/collection

Hypothesis

Experiments/tests

Interpret/revise hypothesis

Conclusion

Observation/collection The investigator examines the crime scene and fills out a report.

Observation/collection

The investigator examines the crime scene and fills out a report.

Observation/collection Hypothesis Experiments/tests Interpret/revise hypothesis Conclusion

Observation/collection

Hypothesis

Experiments/tests

Interpret/revise hypothesis

Conclusion

Hypothesis The investigator imagines several likely scenarios that may have led to to the accident. Maybe the driver was intoxicated, fell asleep or was speeding; maybe mechanical failure or bad weather conditions.

Hypothesis

The investigator imagines several likely scenarios that may have led to to the accident. Maybe the driver was intoxicated, fell asleep or was speeding; maybe mechanical failure or bad weather conditions.

Observation/collection Hypothesis Experiments/tests Interpret/revise hypothesis Conclusion

Observation/collection

Hypothesis

Experiments/tests

Interpret/revise hypothesis

Conclusion

Experiments/tests The investigator might order a blood alcohol level test; check the car parts, test drive the car in different weather conditions to replicate the skid marks left by the car.

Experiments/tests

The investigator might order a blood alcohol level test; check the car parts, test drive the car in different weather conditions to replicate the skid marks left by the car.

Observation/collection Hypothesis Experiments/tests Interpret/revise hypothesis Conclusion

Observation/collection

Hypothesis

Experiments/tests

Interpret/revise hypothesis

Conclusion

Interpret/revise hypothesis The investigator must reexamine evidence and possibly revise his hypothesis. The evidence may be inconclusive.

Interpret/revise hypothesis

The investigator must reexamine evidence and possibly revise his hypothesis. The evidence may be inconclusive.

Observation/collection Hypothesis Experiments/tests Interpret/revise hypothesis Conclusion

Observation/collection

Hypothesis

Experiments/tests

Interpret/revise hypothesis

Conclusion

Conclusion The investigator goes to court, reexamines the evidence, and defends his theory of how the accident occurred.

Conclusion

The investigator goes to court, reexamines the evidence, and defends his theory of how the accident occurred.

The Scientific Method Observation/collection Hypothesis Experiments/tests Interpret/revise hypothesis Conclusion

Observation/collection

Hypothesis

Experiments/tests

Interpret/revise hypothesis

Conclusion

What are the basic SI units for : Newton Joule Watt N = kgm/s 2 J = kgm 2 /s 2 W = kgm 2 /s 3

Newton

Joule

Watt

N = kgm/s 2

J = kgm 2 /s 2

W = kgm 2 /s 3

What do the following represent? d x y m Distance Displacement in the x direction Displacement in the y direction Mass or meter

d

x

y

m

Distance

Displacement in the x direction

Displacement in the y direction

Mass or meter

How about  x  v  p Change in position  x=x f -x i Change in velocity  v=v f -v i Change in momentum  p=p f -p i

 x

 v

 p

Change in position

 x=x f -x i

Change in velocity

 v=v f -v i

Change in momentum

 p=p f -p i

Solve A car travels from city K to city Q (100. km). If the first half of the distance is driven at 50. km/h and the second half is driven at 100. km/h, what is the average speed for the trip? (67 km/h)

A car travels from city K to city Q (100. km). If the first half of the distance is driven at 50. km/h and the second half is driven at 100. km/h, what is the average speed for the trip?

(67 km/h)

Solve A car travels from city K to city Q (100. km). If the first half of the time was at 50. km/h and the second half is spent at 100. Km/h, what is the average speed for the trip? (75 km/h)

A car travels from city K to city Q (100. km). If the first half of the time was at 50. km/h and the second half is spent at 100. Km/h, what is the average speed for the trip?

(75 km/h)

Solve Find the acceleration of an amusement park ride that falls from rest to a speed of 28 m/s in 3.0 s? (9.3 m/s 2 )

Find the acceleration of an amusement park ride that falls from rest to a speed of 28 m/s in 3.0 s?

(9.3 m/s 2 )

Solve Find the acceleration of an Olympic sprinter who runs 100.0 m in 9.74 s. (2.11 m/s 2 )

Find the acceleration of an Olympic sprinter who runs 100.0 m in 9.74 s.

(2.11 m/s 2 )

Solve A bicyclist accelerates from 5.0 m/s to a velocity of 16 m/s in 8 s. Assuming uniform acceleration, what distance does the bicyclist travel during this time interval? (84 m)

A bicyclist accelerates from 5.0 m/s to a velocity of 16 m/s in 8 s. Assuming uniform acceleration, what distance does the bicyclist travel during this time interval?

(84 m)

Solve An aircraft has a landing speed of 302 km/h. The landing area of an aircraft carrier is 195 m long. What is the minimum uniform acceleration required for a safe landing? (-18.0 m/s 2 )

An aircraft has a landing speed of 302 km/h. The landing area of an aircraft carrier is 195 m long. What is the minimum uniform acceleration required for a safe landing?

(-18.0 m/s 2 )

Solve An orange is thrown straight up from the ground at a velocity of 8.7 m/s. What is the orange’s velocity at the end of its flight? (-8.7 m/s)

An orange is thrown straight up from the ground at a velocity of 8.7 m/s. What is the orange’s velocity at the end of its flight?

(-8.7 m/s)

What is the acceleration of the orange at its lowest position? What is the orange’s acceleration at its highest position? How high would the orange go, if there was no air resistance?

What is the acceleration of the orange at its lowest position? What is the orange’s acceleration at its highest position? How high would the orange go, if there was no air resistance?

Solve Billy travels 4.5 km northeast and 4.5 km northwest. What is Billy’s total distance traveled? What is his displacement? (9.0 km, 6.4 km north)

Billy travels 4.5 km northeast and 4.5 km northwest. What is Billy’s total distance traveled? What is his displacement?

(9.0 km, 6.4 km north)

Solve A plane flies 118 km at 15.0 o south of east, then flies 118 km at 35.0 o west of north. Find the total displacement of the plane. (81 km at 55 o north of east)

A plane flies 118 km at 15.0 o south of east, then flies 118 km at 35.0 o west of north. Find the total displacement of the plane.

(81 km at 55 o north of east)

Solve In movies people often jump from buildings into pools. If a person jumps from the 10th floor (30.0 m) to a pool that is 5.0 m away from the building, with what initial velocity must a person jump? (2.0 m/s)

In movies people often jump from buildings into pools. If a person jumps from the 10th floor (30.0 m) to a pool that is 5.0 m away from the building, with what initial velocity must a person jump?

(2.0 m/s)

What is the acceleration of a projectile just before it hits the ground? (-9.81 m/s 2 , the same as at any time during the flight)

What is the acceleration of a projectile just before it hits the ground?

(-9.81 m/s 2 , the same as at any time during the flight)

Solve A flying, stationary kite is acted on by a force of 9.8 N downward. The wind exerts a force of 45 N at an angle of 50.0 o above the horizontal. Find the angle and the force that the string exerts on the kite? (38 N, 40. o below the horizontal)

A flying, stationary kite is acted on by a force of 9.8 N downward. The wind exerts a force of 45 N at an angle of 50.0 o above the horizontal. Find the angle and the force that the string exerts on the kite?

(38 N, 40. o below the horizontal)