Physics ReviewPhysics Review

The Scientific MethodThe 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

• Observation/collection

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

• 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• 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.

• 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• 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.

• 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

• Interpret/revise hypothesis

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

• 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• Conclusion

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

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

The Scientific MethodThe 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 :

What are the basic SI units for :

• Newton• Joule• Watt

• Newton• Joule• Watt

• N = kgm/s2

• J = kgm2/s2

• W = kgm2/s3

• N = kgm/s2

• J = kgm2/s2

• W = kgm2/s3

What do the following represent?

What do the following represent?

• d• x

• y

• m

• d• x

• y

• m

• Distance• Displacement in the

x direction • Displacement in the

y direction• Mass or meter

• Distance• Displacement in the

x direction • Displacement in the

y direction• Mass or meter

How aboutHow about

• x

• v

• p

• x

• v

• p

• Change in position

• x=xf-xi

• Change in velocity

• v=vf-vi

• Change in momentum

• p=pf-pi

• Change in position

• x=xf-xi

• Change in velocity

• v=vf-vi

• Change in momentum

• p=pf-pi

Solve 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 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)

SolveSolve

• 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/s2)

• 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/s2)

SolveSolve

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

• (2.11 m/s2)

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

• (2.11 m/s2)

Solve 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)

SolveSolve

• 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/s2)

• 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/s2)

SolveSolve

• 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?

SolveSolve

• 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)

SolveSolve

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

(81 km at 55o north of east)

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

(81 km at 55o north of east)

SolveSolve

• 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/s2, 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/s2, the same as at any time during the flight)

SolveSolve

• 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 50.0o 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 50.0o above the horizontal. Find the angle and the force that the string exerts on the kite?

• (38 N, 40.o below the horizontal)