Download Review for Final - Lewis-Palmer School District 38

Review Problems for Physics A Final
1. The fastest helicopter, the Westland Lynx, can travel 3.33 km in the forward
direction in just 30.0 s.What is the average velocity of this helicopter? Express
your answer in both meters per second and kilometers per hour. 111 m/s,
400km/hr
2. Eustace drives 20.0 km to the east when he realizes he left his wallet at home.
He drives 20.0 km west to his house, takes 5.0 min to find his wallet, then leaves
again. Eustace is 40.0 km east of his house exactly 60.0 min after he left the first
time.
a.What is his average velocity? 40 km/hr
b.What is his average speed? 80 km/hr
3. A minivan travels along a straight road. It initially starts moving toward the
east. Below is the position-time graph of the minivan. Use the information in the
graph to answer the questions.
1. Does the minivan move to the east? If so, during which time interval(s)? 1040, 60-70
2. Does the minivan move to the west? If so, during which time interval(s)? 4050
3. Is the minivan’s speed between t1 and t2 greater than, less than, or equal to its
speed between t2 and t3? Greater than.
4. Is the minivan’s speed between t4 and t5 greater than, less than, or equal to its
speed between t6 and t7? Greater than.
5. Does the minivan ever stop completely? If so, at which time(s)? 0-10, 50-60
6. Does the minivan ever move with a constant velocity? If so, at which time(s)?
10-20, 20-40, 40-50, 60-70
7. What is the total displacement of the minivan during the trip? -5m
4. Read the book. It will help you with concepts.
5. A gumdrop is released from rest at the top of the Empire State Building, which
is 381 m tall. Disregarding air resistance, calculate the displacement of the
gumdrop after 1.00, 2.00, and 3.00 s.
4.9m, 19.6m, 44.1m
6. A small sandbag is dropped from rest from a hovering hot-air
balloon. After 2.0 s, how far below the balloon is the sand bag? 19.6m
7. A physics student throws a softball straight up into the air with a speed of 17.5
m/s. The ball is in the air for a total of 3.60 s before it is caught at its original
position. How high does the ball rise? 15.625m
8. A surface probe lands on a highland region of the planet Mercury. A few hours
later the ground beneath the probe gives way and the probe falls, landing below
its original position with a velocity of 11.2 m/s downward. If the free-fall
acceleration near Mercury’s surface is 3.70 m/s2 downward, what is the probe’s
displacement? -16.95m
9. A ball thrown vertically is caught by the thrower after 5.1 s. Find the
maximum height the ball reaches. 31.86m
10. Find the initial velocity with which the ball in problem 6 is thrown. 24.99m/s
11. An archer fires an arrow directly upward, then quickly runs from the
launching spot to avoid being struck by the returning arrow. If the arrow’s initial
velocity is 85.1 m/s upward how long does the archer have to run away before
the arrow lands? 17.37s
12. A popular scene in recent action films shows a character in free-fall speed up
to catch a freely falling parachute. Suppose a packed parachute is dropped from
rest from an airplane and that a daredevil is launched straight down from the
plane 3.00 s later. Neglecting air resistance, the daredevil catches up to the
parachute 4.00 s after the daredevil leaves the plane. What are the daredevil’s
initial and final velocities? Initial = 40.4m/s, Final = 79.6m/s
13. The elevators in the Landmark Tower in Yokohama, Japan, are
among the fastest in the world. They accelerate upward at 3.125 m/s2
for 4.00 s to reach their maximum speed. Suppose an empty elevator is
moving upward with its maximum speed when the cable breaks, so that
the elevator slows down, comes to a stop, and then begins to fall freely.
What will the elevator’s velocity be 0.00 s, 1.00 s, 2.00 s, and 3.00 s
after the cable breaks?
12.5m/s, 2.7m/s, -7.1m/s, -16.9m/s
16. A thoroughbred racehorse accelerates uniformly at 7.56 m/s2, reaching its
final speed after running 19.0 m. If the horse starts at rest, what is its final speed?
16.97 m/s
17. A soccer ball moving with an initial speed of 1.8 m/s is kicked with a uniform
acceleration of 6.1 m/s2, so that the ball’s new speed is 9.4 m/s. How far has the
soccer ball moved? 6.9m
18. A dog runs with an initial velocity of 1.50 m/s to the right on a waxed floor. It
slides to a final velocity of 0.30 m/s to the right with a uniform acceleration of
0.35 m/s2 to the left. What is the dog’s displacement? 3.09m
19. A hippopotamus can run up to 30 km/h, or 8.33 m/s. Suppose a
hippopotamus uniformly accelerates 0.678 m/s2 until it reaches a top
speed of 8.33 m/s. If the hippopotamus has run 46.3 m, what is its
initial speed? 2.57 m/s
20. A toy parachute is dropped from an open window that is 13.0 m
above the ground. If the parachute travels 9.0 m horizontally, what is
the resultant displacement? 15.8m, 55° below horizontal
21. The Palm Springs Aerial Tramway extends 3.88 km from the
Valley Station, which is located 0.8 km above sea level, to the
Mountain Station atop San Jacinto Peak. The actual path of the
tramway’s cables is not along a straight line, but if it were, the
horizontal displacement of the tramway would be 3.45 km. How far is
San Jacinto Peak above sea level? 2.57m
22. U.S. Highway 212 extends 55 km at 37° north of east between
Newell and Mud Butte, South Dakota. It then continues for 66 km
nearly due east from Mud Butte to Faith, South Dakota. If you drive
along this part of U.S. Highway 212, what will be your total
displacement? 114km, 16.9° N of E
23. An Arctic tern flying to Antarctica encounters a storm. The tern
changes direction to fly around the storm. If the tern flies 46 km at 15°
south of east, 22 km at 13° east of south, and finally 14 km at 14° west
of south, what is the tern’s resultant displacement? 65km 45.6° S of E
24. In 1977, a helicopter at the heliport atop the 59-story Pan Am
building in New York fell over, causing the rapidly-turning rotor
blades to splinter. One of these fragments landed about 101 m away,
near the corner of Madison Avenue and 43rd Street. Suppose the
fragment moved off the building horizontally with a speed of 14.25
m/s. Use this information to find the height of the Pan Am building.
246.16m
25. A lunch pail is accidentally kicked off a steel beam on a building
under construction. Suppose the initial horizontal speed is 1.50 m/s.
How far does the lunch pail fall after it travels 3.50 m horizontally?
26.7m
26. A baseball is thrown with an initial speed of 15.0 m/s. If the ball’s
horizontal displacement is 17.6 m, at what angle with respect to the
ground is the ball pitched? 25°
27. A shingle slides down a roof having a 30.0° pitch and falls off with
a speed of 2.0 m/s. How long will it take to hit the ground 45 m below?
2.93s
28. A ball is thrown from a roof with a speed of 10.0 m/s and an angle
of 37.0° with respect to the horizontal. What are the vertical and
horizontal components of the ball’s displacement 2.5 s after it is
thrown? Horizontal 20m, Vertical -15.58m
29. A bird flies directly into a wind. If the bird’s forward speed relative
to the wind is 58.0 km/h and the wind’s speed in the opposite direction
is 55.0 km/h, relative to Earth, how long will it take the bird to fly 1.4
km? .467 hr
30. An airship moving north at 55.0 km/h with respect to the air
encounters a wind from 17.0° north of west. If the wind’s speed with
respect to Earth is 40.0 km/h, what is the airship’s velocity with respect
to Earth? 57.78 km/hr, 41.5° N of E
31. A sailboat travels south with a speed of 12.0 km/h with respect to
the water. Suppose the boat encounters a current that has a velocity
with respect to Earth of 4.0 km/h at 15.0° south of east. What is the
sailboat’s resultant velocity with respect to Earth? 13.59km/hr, 73° S of
E
32. Three workers move a car by pulling on three ropes. The first
worker exerts a force of 6.00 . 102 N to the north, the second a force of
7.50 . 102 N to the east, and the third 6.75 . 102 N at 30.0° south of
east. In what precise direction does the car move? 1360N, 11.12° N of
E
33. A shopper pushes a grocery cart by exerting a force on the handle.
If the force equals 76 N at an angle of 40.0° below the horizontal, how
much force is pushing the cart in the forward direction? What is the
component of force pushing the cart against the floor? 58.21N, 48.85N
34. A traffic signal is supported by two cables, each of which makes an
angle of 40.0° with the vertical. If each cable can exert a maximum
force of 102 N, what is the largest weight they can support? 131.13N
35. Suppose an empty grocery cart rolls downhill in a parking lot. The
cart undergoes a constant increase in speed of 1.0 m/s over a 5.0 s
interval. If the downhill force acting on the cart is 18.0 N and the
uphill force due to friction is 15.0 N, what is the cart’s mass? 15kg
36. A 214 kg boat is sinking in the ocean. The boat’s weight is partially
offset by the 790 N buoyant force of the water. What is the net
acceleration of the boat? 6.1 m/s2
37. A 90.0 kg skier glides down a slope with an incline of 17.0°.What
frictional force is needed for the skier to move at a constant velocity?
257.9N
38. A snowboarder slides down a 5.0° slope at a constant speed. What
is the coefficient of kinetic friction between the snow and the board?
.083
39. A 25 kg box is pushed across a floor. The coefficients of friction are 0.9 and
0.65 for static and kinetic. How much force is required to break it loose and
what is the acceleration of the box after it is sliding? 220N, 2.45m/s2
40. A building under construction requires building materials to be raised to the
upper floors by cranes or elevators. An amount of cement is lifted 76.2 m by a
crane, which exerts a force on the cement that is
slightly larger than the weight of the cement. If the net work done on
the cement is 1.31 × 103 J, what is the magnitude of the net force
exerted on the cement? 17.19N
41. A car has run out of gas. Fortunately, there is a gas station nearby.
You must exert a force of 715 N on the car in order to move it. By the
time you reach the station, you have done 2.72 × 104 J of work. How
far have you pushed the car? 38N
42. A 50.0 kg parachutist falls at a speed of 47.00 m/s when the
parachute opens. The parachutist’s speed upon landing is 5.00 m/s.
How much work is done by the air to reduce the parachutist’s speed?
54,600J
43. A 5.0 kg stone is slid up a frictionless ramp that has an incline of
25.0°. How long is the ramp if the gravitational potential energy
associated with the stone is 2.4 × 102 J? 11.59m
44. What would be the kinetic energy of a 0.500 g raindrop if it fell
0.250 km without any resistance provided by air? 1.225J
45. A toy rocket is at a height of 75.0 m and is moving upward with a speed of
1.2 m/s when it ejects a payload with a mass of 20.0 g. The payload has an initial
upward speed relative to the rocket of 3.5 m/s.
What is the height reached by the payload when its upward velocity is
zero? 76.13m
46. A 100.0 g arrow is pulled back 30.0 cm against a bowstring. If the
spring constant of the bowstring is 1250 N/m, at what speed will the
arrow leave the bow? 33.54 m/s
47 If you were to neglect air resistance, a projectile fired straight up into the air
would land again with the speed with which it was fired. (This is why it is
dangerous to shoot a bullet directly upward.) However, some of the energy is lost
because of air resistance. Suppose a 50.0 g projectile
is fired upward with an initial speed of 3.00 × 102 m/s. If it lands with
a speed of 89.0 m/s, how much mechanical energy is given up because
of air resistance? 2051.975J
48. Although it cannot sustain its top speed for more than 8.65 s, the
cheetah can run a distance of 274 m during that time. If a cheetah with
a mass of 50.0 kg is moving north at its top speed, what is its
momentum? 1583.8 kgm/s
49. A net force of 10.0 N to the right pushes a 3.0 kg book across a
table. If the force acts on the book for 5.0 s, what is the book’s final
velocity? Assume the book to be initially at rest. 16.67m/s
50. How much time would it take for a 0.17 kg ice hockey puck to
decrease its speed by 9.0 m/s if the coefficient of kinetic friction
between the ice and the puck is 0.050? 18.38s
51. A 63 kg astronaut drifting with 7.0 m/s to the right with respect to a
spacecraft uses a jet pack to slow down. If it takes 14.0 s to come to a
stop with respect to the spacecraft, what is the force exerted by the jet
pack? How far does the astronaut travel before stopping? 31.5N, 49m
52. A 0.5 kg tetherball is traveling at 3 m/s when struck in the opposite direction
for 0.3 s. It is now traveling at 5 m/s back the way it came. What was the
force of the blow? 13.33N
53. A 1550 kg torpedo strikes a 770 kg target that is initially at rest. If
the combined torpedo and target move forward with a speed of 9.44
m/s, what is the initial velocity of the torpedo? Assume that no
resistance is provided by the water. 14.13m/s
54. A railway car with a mass of 8500 kg and a velocity of 4.5 m/s to
the right collides inelastically with a railway car with a mass of
9800 kg and a velocity of 3.9 m/s to the left. What is the final
velocity of the combined cars? ≈ 0
55. Two flying fish have an inelastic collision while in mid-flight. One
fish has a mass of 0.650 kg and a velocity of 15.0 m/s to the right; the
other has a mass of 0.950 kg and a velocity of 13.5 m/s to the left. Find
the change in their kinetic energy after the collision. -156.73 J