A person jogs eight complete laps around a 400-m track in a total time of 15.5 min .

Embry-Riddle Aeronautical University Department of Physical Sciences

Home Work # 3 PS 103 � Technical Physics�I

Due Date: Sep 22, 2014 (Monday)

Name:

Date: September 15, 2014 (Monday)

Semester: Fall-2014

Section:

Total point: 10

Important:

• Home work is due in the beginning of the class on the date mentioned above.

• Please note that providing answers without showing any working will not qualify as correct. So to get full points show EACH AND EVERY STEP.

• Please answer all questions neat and clean in as much detail as you can.

• All the conventions followed in the homework are same as that of lectures.

Question# 1:- Some easy questions

a) What must your car’s average speed be in order to travel 235 km in 2.75 h?

b) A particle at t1 = –2.0 s is at x1 = 4.8 cm and at t2 = 4.5 s is at x2 = 8.5 cm. What is its average velocity over this time interval? Can you calculate its average speed from these data? Why or why not?

c) A bird can fly 25 km/h. How long does it take to fly 3.5 km?

d) A person jogs eight complete laps around a 400 m track in a total time of 14.5 min. Calculate (I) the average speed and (II) the average velocity, in m/s.

e) Two locomotives approach each other on parallel tracks. Each has a speed of 155 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other?

f) A sprinter accelerates from rest to 9.00 m/s in 1.38 s. What is her acceleration in (I) m/s2; (II) km/h2?

g) A sports car accelerates from rest to 95 km/h in 4.3 s. What is its average acceleration in m/s2?

h) At highway speeds, a particular automobile is capable of an acceleration of about 1.8 m/s2. At this rate, how long does it take to accelerate from 65 km/h to 120 km/h?

Question# 2:- A plane flies from base camp to lake A, a distance of 280 km at a direction of 20.0� north of east. After dropping o↵ supplies, the plane flies to lake B, which is 190 km and 30.0� west of north from lake A. Determine the distance and direction from lake B to the base camp.

Question# 3:- A rural mail carrier leaves the post o�ce and drives 22.0 km in a northerly direction. She then drives in a direction 60.0� south of east for 47.0 km. What is her displacement from the post o�ce?

Question# 4:- Some easy questions

a) If v x

= +9.80 units and v y

= +6.40 units, determine the magnitude and direction of ~v.

b) If v x

= +9.80 units and v y

= �6.40 units, determine the magnitude and direction of ~v. c) If v

x

= �9.80 units and v y

= +6.40 units, determine the magnitude and direction of ~v.

d) If v x

= �9.80 units and v y

= �6.40 units, determine the magnitude and direction of ~v.

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Embry-Riddle Aeronautical University

Question# 5:- A stone is thrown vertically upward with a speed of 15.5 m/s from the edge of a cli↵ 75.0 m high (Figure 1).

a) How much time will it take to reach the highest point?

b) What is its velocity at the highest point?

c) How much later does it reach the bottom of the cli↵ after it was thrown upward?

d) What is its speed just before hitting?

e) What total distance did it travel?

f) How much time will it remain in air?

g) How much time will it take to reach the highest point?

h) What total displacement of the stone?

h) What is the speed of the stone when it is 50 m below the cli↵’s top?

i) What is the speed of the stone when it is 1 m above the cli↵’s top?

j) What total displacement of the stone? Figure 1: Problem-5

Question# 6:- An airplane trip involves three legs, with two stopovers, as shown in Figure 2. The first leg is due east for 620 km; the second leg is south- east (45�) for 440 km; and the third leg is at 53�

south of west, for 550 km, as shown. What is the plane’s total displacement (do not forget that dis- placement is a vector quantity you need to calculate its magnitude as well as direction fot it’s complete discription)?

Figure 2: Problem-6

Question# 7:- Three vectors are shown in Figure 3. Their magnitudes are given in arbitrary units. De- termine the sum of the three vectors. Give the re- sultant in terms of

a) components,

b) magnitude and angle with the ± x�axis. c) vector form.

Figure 3: Problem-7

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Question# 8:- A Pakistani rescue plane drops a pack- age of emergency rations to a stranded hiker, as shown in Figure 4. The plane is traveling horizon- tally at 40.0 m/s at a height of 1.00⇥ 102 m above the ground.

a) What are the horizontal and vertical compo- nents of the velocity of the package just after it is droped from the plane?

b) How much time will the package take to reach the surface of the ground.

c) Where does the package strike the ground rel- ative to the point at which it was released?

d) What are the horizontal and vertical compo- nents of the velocity of the package just before it hits the ground?

e) Where will be the plane at the time when the package just hits the ground? Figure 4: Problem-8

Question# 9:- A stone is thrown upward from the top of a building at an angle of 30.0� to the horizontal and with an initial speed of 20.0 m/s, as in Figure 5. The point of release is 45.0 m above the ground.

a) What are the horizontal and the virtical com- ponents of the initial velocity?

b) How much the time will the stone take to reach the maximum hight?

c) What is the maximum hight of the stone from the top of the building?

d) How long does it take for the stone to hit the ground from the time of throwing (how much time it spend in air)?

e) Find the stone’s speed at impact.

f) Find the horizontal range of the stone which is shown in the figure as x.

Figure 5: Problem-9

Question# 10:- A daredevil is shot out of a cannon at 45.0� to the horizontal with an initial speed of 25.0 m/s. A net is positioned a horizontal distance of 50.0 m from the cannon. At what height above the cannon should the net be placed in order to catch the daredevil?

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