Iona Prep Physics
Problems from the textbook |

50. [modified](A) Light from the Sun reaches earth in 8.3 minutes. How far is the earth from the sun? (You will need to use reference material). (B) How long will it take a radio message to travel from the earth to the moon? (Radio waves travel at the speed of light).

51. A car is moving down the street at 55 km/hr. A child suddenly runs into the street. If it takes the driver 0.75 s to react and apply the brakes, how many meters will the car have moved before it begins to slow down?

53. You and a friend each drive 50.0 km. You travel at 90.0 km/h. Your friend travels at 95.0 km/h. How long will your friend have to wait for you at the end of the trip?

9. A bus is moving at 25 m/s when the driver steps on the brakes and brings the bus to a stop in 3.0 s.

(a) What is the average acceleration of the bus while braking?

(b) If the bus took twice as long to stop, how would the acceleration compare with what you found in part a?

Page 65

19. A bus that is traveling at 30 km/h speeds up at a constant rate of 3.5
m/s^{2} .

What velocity does it reach 6.8 s later?

20. If a car accelerates from rest at a constant 5.5 m/s^{2}, how long will
it take for the car to reach a velocity of 28 m/s?

21. A car slows from 22 m/s to 3.0 m/s at a constant rate of 2.1 m/s^{2}.

How many seconds are required before the car is traveling at 3.0 m/s?

Page 71 A slight challenge

#30 A man runs at a velocity of 4.5 m/s for 15 min. When going up an increasingly
steep hill, he slows down at a constant rate of 0.05 m/s^{2} for 90
seconds and comes to a stop. How far did he run?

#32 You start your bicycle ride at the top of a hill. You coast down the hill
at a constant acceleration of 2.0 m/s^{2}. When you get to the bottom
of the hill you are moving at 18 m/s and you pedal to maintain that speed. If
you continue at this speed for 1.0 minute, how far will you have gone from the
time you left the hilltop?

Page 74

#42 A construction worker accidentally drops a brick from a high scaffold. (A) What is the velocity of the brick after 4.0 sec? (B) How far does the brick fall during that time?

Page 82

#90 A race car can be slowed with a constant acceleration of -11m/sec^2. If the car is travelling at 55 m/s how many meters will it take to stop? How many feet would that be?

A Major challenge:

Similar to page 82 number 94

A speeding car is traveling at a constant speed of 30.0 m/s when it passes
a stopped police car. The police car accelerates at 7.0 m/s^{2}. How
long will it take for the police car to catch up with the speeding car?

# 115 A helicopter is rising at 5.0 m/s when a bag of its cargo is dropped. The bag falls for 2.0 seconds. (A) What is the bag's velocity at the end of the 2 sec? (B) How far has the bag fallen during the 2 sec? (C) How far below the heloicopter is the bag at the end of 2 sec?

Page 97

16. Kamaria is learning how to ice-skate. She wants her mother to pull her
along so that she has an acceleration of 0.80 m/s^{2}. If Kamaria's
mass is 27.2 kg, with what force does her mother need to pull her? Assume there
is no friction between her skates and the ice.

17. Two people simultaneously grab a 0.75 kg piece of rope and begin pulling
on it in opposite directions. If one pulls with a force of 16 N, and the rope
accelerates in the opposite direction, at 1.25 m/s^{2}, with what force
is the other person pulling?

19. On Earth, a scale shows that you weigh 585 N. (a) What is your mass? (b)
What would be the scale reading on the Moon (g=1.6 m/s^{2}?)

## A box of mass 10 kilograms is resting on a level surface.

What is the weight of the box?

If there is a string applying an upward force of 50 N to the box, what force
must the force between the box and the surface?

If there were a string applying an upward force of 150 N to the box, calculate
the acceleration of the box.

Page101

#22 You take a ride in a fast elevator to the top of a tall building and ride back down while standing on a bathroom scale. During which parts of the ride will your apparent and real weights be the same? During which parts will your apparent weight be less than your real weight? More than your real weight?

#24 You are riding in an elevator holding a spring sale with a 1 kg mass suspended from it. You look at the scale and see that it reads 9.3 N. What, if anything can you conclude about the elevator's motion at the time?

#26 A sky diver falls at a constant speed in the spread-eagle position. After he opens his parachute, is the sky diver accelerating? If so, in which direction?

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#32. You are helping to repair a roof by loading equipment into a bucket that workers hoist to the rooftop. If the rope is guaranteed not to break as long as the tension does not exceed 450 N and you fill the bucket until it has a mass of 42 kilograms, what is the greatest acceleration that the workers can give the bucket as they pull it to the roof?

## When you stand on a scale in an elevator which is stationary, it reads 784
N.

What is your mass?

What will the scale read if you are moving up at a constant velocity of 3 m/s?

What will the scale read if you are moving down at a constant velocity of 3
m/s?

What will the scale read if you are accelerating up at 2m/s^{2}?

What will the scale read if you are accelerating down at 2 m/s^{2}?

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# 64 Your new motorcycle weighs 2450 N. What is its mass in kilograms?

#67 You place a 7.5 kg television on a scale and it weighs 78.4 N. What is the acceleration of gravity at that location?

#75 A 6.0 block rests on top of a 7.0 kilogram block which rests on a horizontal table. (a) What is the force exerted by the 7.0 kg block on the 6.0 kg block? (b) What is the force exerted by the 6.0 kg block on the 7.0 kilogram block (give magnitude and direction of each of the forces).

#79 A 4500 kg helicopter accelerates upward at 2.0 m/s^{2}. What is
the magnitude of the lift force exerted by the air on the propellers?

#84 Suppose a 65 kg. boy and a 45 kg. girl use a massless rope in a tug-of-war
on an icy resistance-free surface. If the acceleration of the girl toward the
boy is 3.0 m/s^{2} find the acceleration of the boy toward the girl.

#86 As a baseball is being caught, its speed goes from 30.0 m/s to rest in about 0.0050 s. The mass of the baseball is 0.145 kilograms. (a) What is the baseball's acceleration? (b) What are the magnitude and direction of the force acting on it? (c) Whart are the magnitude and direction of the force acting on the player who caught it?

#88 A student stands on a bathroom scale in an elevator at rest on the 64th. floor of a building. The scale reads 836 N. (a) As the elevator moves up the scale reading increases to 936 N. What is the acceleration of the elevator? (b) As the elevator approaches the 74th. floor, the scale reading drops to 782 N. What is the acceleration of the elevator?

#96 Three blocks are connected by massless strings and are pulled along a frictionless horizontal surface toward the right by a force of 36.0 which is applied to the first block which has a mass of 6.0 kg. The first block is connected to the second by a string. The tension in that string is T2. The second block has a masss of 4.0 kilograms and is connected to the third block by another string. The tension in the second string is T1. The last block has a mass of 2.0 kilograms. Find the acceleration of each block and the tension forces T1 and T2.

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1. A car is driven 125 km due west then 65 km due east. What is the magnituede of its displacement?

3. A hiker walks 4.5 km due north then makes a 45 degree turn to the West and walks another 6.4 km. What is the magnitude of the resultant displacement?

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7. You walk 8.0 km due north from home and then walk east until your displacement
from home is 10.0 km. How far east did you walk?

Momentum and its Conservation:

Use the Momentum Applet to answer the following questions:

1. Elastic Collision: (e=1) If the red block has a mass of 1.0 kg and moves at 5.0 m/s and the green block has a mass of 2 kg and moves at -5 m/s, what are the speeds of the red and green blocks after the collision?

Momentum

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# 67

A 0.145 kg baseball is moving at 35 m/s when it is caught by a player.

a.Find the change in momentum of the ball

b.If the ball is caught with the mitt held in a stationary position so that
the ball stops in 0.050s, what is the average force exerted on the ball?

c. If instead the mitt is moving backward so that the ball takes 0.50 s to stop,
what is the average force exerted by the mitt on the ball?

#68

A hockey puck has a mass of 0.115 kg and strikes the pole of the net at 37 m/s
and bounces back in the opposite direction at 25 m/s. What is the impulse on
the puck? If the collision takes 5.0x10^-4 s what is the average force on the
puck?

#73

A 95 kg (209 lb) fullback running at 8.2 m/s collides in midair with a 128 kg
(282 lb) defensive tackle moving in the opposite direction. Both players end
up with zero speed. How fast was the defensive tackle moving originally?

#74

Marble C with mass 5.0 g moves at a speed of 20 cm/s. It collides with a second
marble D with mass 10.0g moving at 10 cm/s in the same direction. After the
collision, marble C continues with a speed of 8.0 cm/s in the same direction.

What is the speed of marble D after the collision?

#76

A 50.0 g projectile is launched with a horizontal velocity of 647 m/s from a
4.65 kg launcher moving in the same direction at 2.0 m/s. What is the launcher's
velocity after the launch?

#86

A 0.115 kg hockey puck, moving at 35.0 m/s strikes a .365 kg jacket that is
thrown onto the ice by a fan. The puck and jacket slide off together. Find their
speed.

#90

A 92 kg fullback running at 5.0 m/s attempts to dive directly across the goal
line for a touchdown. Just as he reaches the line, he is met head-on in mid
air by two 75 kg linebackers, both moving in the opposite direction. One is
moving at 2.0 m/s and the other at 4.0 m/s. They all become entangled as one
mass.

Does the fullback score a touchdown?