Fall 2005 Physics 101 Hour Exam 1
(24 questions)

The grading button and a description of the scoring criteria are at the bottom of this page. Basic questions are marked by a single star *. More difficult questions are marked by two stars **. The most challenging questions are marked by three stars ***.

True-false questions are worth 2 points each, three-choice multiple choice questions are worth 3 points each, five-choice multiple choice questions are worth 6 points each. The maximum possible score is 95. The exam period was 90 minutes; the mean score was 65.8; the median score was 68. Click here to see page1 page2 of the formula sheet that came with the exam.


QUESTION 1*

This and the following two questions concern the same physical situation.

A 7 kg block is held by three strings as shown in the figure below. The string on the left is pulling horizontally with a force of 233 N. The string in the center pulls down with a force of 50 N, and the string on the right pull at an unknown angle q. (Gravity acts in the vertical direction.)

What is the horizontal component of the tension in the right string?

(a)   TRx = 164 N
(b)   TRx = 183 N
(c)   TRx = 233 N


QUESTION 2*

What is the vertical component of the tension in the right string?

(a)   TRy = 50.2 N
(b)   TRy = 68.9 N
(c)   TRy = 118.6 N
(d)   TRy = 159.0 N
(e)   TRy = 233.5 N


QUESTION 3***

If the tension in the center string, TC, is increased from 50 N to 75 N, the tension in the left string TL will (note: the angles of the 3 strings will not change when this tension is increased)

(a)   increase.
(b)   remain unchanged.
(c)   decrease.


QUESTION 4*

This and the following three questions concern the same physical situation.

A person kicks a football (initially on the ground) towards a field goal 35 meters away. As a result of the kick, the ball leaves the ground at an angle of 35 degrees above horizontal with a speed of 20 m/s.

What is the y-component of the acceleration of the ball when it is at the top of its trajectory?

(a)   ay = - 9.8 m/s2
(b)   ay = 0 m/s2
(c)   ay = + 9.8 m/s2


QUESTION 5**

What is the speed | v | of the ball when it is at the top of its trajectory?

(a)   | v | = 0
(b)   | v | = 16.4 m/s
(c)   | v | = 20 m/s


QUESTION 6*

Calculate ymaxthe maximum height the ball reaches.

(a)   ymax = 6.7 m
(b)   ymax = 8.3 m
(c)   ymax = 9.5 m
(d)   ymax = 11.0 m
(e)   ymax = 20.4 m


QUESTION 7*

Calculate d the horizontal distance the ball travels before hitting the ground.

(a)   d = 15 m
(b)   d = 21 m
(c)   d = 38 m
(d)   d = 43 m
(e)   d = 47 m


QUESTION 8**

This and the following question concern the same physical situation.

You are on the surface on an unknown planet of radius R = 1.5 × 106 m. You notice that if you throw a ball horizontally at 35 m/s, it goes completely around the planet hitting you in the back 270,000 seconds later with exactly the same speed that you originally threw it.

As the ball traveled around the planet its acceleration was zero.

(T)   True
(F)   False


QUESTION 9**

What is the mass of the planet?

(a)   1.3 × 1019 kg
(b)   2.1 × 1019 kg
(c)   2.8 × 1019 kg


QUESTION 10*

This and the following question concern the same physical situation.

A washing machine on the spin cycle spins the tub with an angular velocity of 30 radians/second. A person opens the door, and the tub comes to rest after spinning an additional 270 radians. (Assume constant acceleration.)

What is the magnitude of the angular acceleration of the tub after the door is opened?

(a)   1.67 radians/s2
(b)   2.93 radians/s2
(c)   9.18 radians/s2


QUESTION 11*

How long does it take for the tub to come to a complete stop after the door is opened?

(a)   4 seconds
(b)   18 seconds
(c)   37 seconds


QUESTION 12***

An airplane flies with a velocity relative to the air of 150 m/s due east. The wind is blowing with a speed of 50 m/s at an angle 45 degrees north of west. What is the speed of the plane relative to the ground?

(a)   100 m/s
(b)   115 m/s
(c)   120 m/s
(d)   155 m/s
(e)   185 m/s


QUESTION 13**

This and the following question concern the same physical situation.

Three boxes, A of mass 4 kg, B of mass 2 kg, and C of mass 3 kg, are connected together by mass-less strings, as shown in the figure. They are resting on a horizontal, frictionless surface and the whole assembly is being pulled to the right, as shown in the figure. The tension T1 = 36 N.

Calculate the tension T2.

(a)   T2 = 36 N
(b)   T2 = 20 N
(c)   T2 = 16 N
(d)   T2 = 12 N
(e)   T2 = 8 N


QUESTION 14**

What is the magnitude of the net force on block B?

(a)   8 N
(b)   14 N
(c)   20 N


QUESTION 15*

This and the following question concern the same physical situation.

An arrow is shot vertically upwards.

At the moment it reaches its maximum height, the acceleration of the arrow is(note: positive acceleration is upwards and negative acceleration is downwards towards the Earth)

(a)   a < 0
(b)   a = 0
(c)   a > 0


QUESTION 16*

At the moment it reaches its maximum height, the velocity of the arrow is (note: positive velocity is up and negative velocity is down towards the Earth)

(a)   v < 0
(b)   v = 0
(c)   v > 0


QUESTION 17*

This and the following question concern the same physical situation.

A bicyclist travels a route through the countryside around Champaign-Urbana. She starts from point A, riding 6 miles due north, then 10 miles east. After stopping for a break of an hour, she resumes her journey by riding 12 miles south, then 2 miles west. This point in her journey is designated B.

At point B in her journey what is the magnitude of her displacement from her starting point A?

(a)   10 miles
(b)   20 miles
(c)   30 miles


QUESTION 18**

If she starts her journey from point A at 8 am and arrives at point B at 12 noon, what is the magnitude of her average velocity for this journey?

(a)   10.0 mph
(b)   5.0 mph
(c)   2.5 mph


QUESTION 19**

This and the following two questions concern the same physical situation.

Box A of mass MA=5 kg is suspended by a massless cord over a massless pulley and connected to a second box B that sits on an incline. The incline is at an angle of 30 degrees with the horizontal, as shown in the figure.

If the boxes are resting in equilibrium, with neither moving up or down, what is the mass of box B, assuming that there is no friction between it and the surface on which it sits?

(a)   5.00 kg
(b)   5.77 kg
(c)   10.00 kg


QUESTION 20**

Now assume that box B is replaced by a box with unknown mass MB and coefficient of kinetic friction μk = 0.2 . This new box is observed to accelerate up the ramp at 5 m/s2.

Calculate the tension in the string as the block accelerates up the ramp?

(a)   T = 20 N
(b)   T = 24 N
(c)   T = 49 N


QUESTION 21**

Calculate the mass MB of the block B.

(a)   MB = 0.5 kg
(b)   MB = 1 kg
(c)   MB = 2 kg
(d)   MB = 5 kg
(e)   MB = 10 kg


QUESTION 22*

A flat-bed truck is loaded with a large crate that is not tied down. The crate just sits on the flat-bed. The coefficient of static friction between the truck bed and the crate is μ = 0.35. What is the magnitude of the maximum possible acceleration of the truck on a horizontal road that will not cause the crate to slip backwards?

(a)   1.72 m/s
(b)   3.43 m/s
(c)   5.21 m/s
(d)   7.44 m/s
(e)   8.03 m/s


QUESTION 23**

This and the following question concern the same physical situation.

An astronaut is strapped into a rocket that has just been launched vertically upwards. Just after liftoff the acceleration of the rocket is 3g, where g = 9.80 m/s2. If the weight of the person while stationary on the Earth’s surface is 750 N, his apparent weight at this time is

(a)   750 N
(b)   1500 N
(c)   3000 N


QUESTION 24***

After a while the rocket reduces thrust such that it travels with a constant velocity. How far will the astronaut be above the surface of the Earth when his weight is 30 Newtons? Assume that the Earth radius is exactly 6,000 km.

(a)   6,000 km
(b)   12,000 km
(c)   24,000 km
(d)   30,000 km
(e)   42,000 km