# Physics exam

DURATION: 90 minutes

1. Read this instructions page and sign it near the bottom.
2. This is a closed-book test.
3. Only non-programmable and non-graphic calculators are allowed.
4. All cell phones and pagers must be switched off and placed in the bags in the front of the room.
5. Put your Ryerson photo ID on the desk.
6. Talking to another student or glancing over another student’s paper is not permitted and it may result in a charge of academic misconduct.

There are 15 multiple choice questions.  Each multiple-choice question is worth 1 mark.

• Show all your work in this booklet. We may check your work, and if your answer is not justified by it, credit will not be given.
• Some answers are rounded off a little bit so don’t panic! Select the option that is numerically closest to your answer, circle it in this booklet.
• The correct response gets full marks and an incorrect response or no response gets no marks.
• If more than one selection is made in answer to a question, you will not get any credit for that question.

Please sign here indicating you have read and understood the above instructions.

DO NOT OPEN THIS BOOKLET UNTIL YOU ARE TOLD TO DO SO.

Then, before you start writing, verify that you do have all 5 pages (otherwise, inform the invigilators).

1. The average distance a gas molecule travels before colliding with another molecule is called the “mean free path” which we denote as . The mean free path depends on two things: the number density of air molecules  which has dimensions , and the cross sectional area of the gas molecules (denoted as 𝜎).  By analyzing dimensions and units, determine which of the following could be the correct formula for mean free path.

1. ℓ = 𝑛 𝜎
2. ℓ = 𝑛/𝜎
3. ℓ = 1/(𝑛𝜎)

1. Convert 120 dollars/yard2 in euro/m2. (1 euro = 1.44 dollar, 0.9144 m = 1 yard)

1. 207
2. 189
3. 158
4. 144
5. 100

1. Vector A has a magnitude of 25.0 cm and points at 30.0° above the positive x-axis. Vector B has a magnitude of 55.0 cm and points along the negative x-axis.  Determine the magnitude and direction of the sum of these two vectors.

1. 9 cm at 28.2° above the positive x-axis
2. 5 cm at 28.2° above the negative x-axis
3. 9 cm at 19.1° above the positive x-axis
4. 1 cm at 33.8° above the negative x-axis
5. 1 cm at 33.8° above the positive x-axis

1. At one particular moment, a subway train is moving with a negative velocity and a negative acceleration. Which of the following phrases best describes the motion of this train?  Assume the front of the train is pointing in the positive x direction.

1. The train is moving forward as it slows down.
2. The train is moving in reverse as it slows down.
3. The train is moving faster as it moves forward.
4. The train is moving faster as it moves in reverse.
5. The train is moving at a constant speed.

1. A plane pilot performs a circular dive of radius 800 m. At the bottom of the dive (point B in the figure) the pilot has a speed of 200 m/s which at that instant is increasing at a rate of 20 m/s2.  What acceleration does the pilot have at point B?

1. (50i + 20j) m/s2
2. (20i − 50j) m/s2
3. (20i + 50j) m/s2
4. (−20i + 50j) m/s2
5. (−50i + 20j) m/s2

1. You swing a bat and hit a heavy box with a force of 1500 N. The force the box exerts on the bat is

1. exactly 1500 N only if the box does not move.
2. exactly 1500 N whether or not the box moves.
3. greater than 1500 N if the box moves.
4. less than 1500 N if the box moves.
5. greater than 1500 N if the bat bounces back.

1. A woman is pushing a box with a constant horizontal force 𝐹0. As a result, the box moves across the horizontal floor at a constant speed 𝑣0.  If the woman doubles the magnitude of her pushing force to 2𝐹0, which of the following is the best description of the box’s motion?

1. It continues to move with a constant speed 𝑣0.
2. It moves with a constant speed 2𝑣0.
3. It moves with a constant speed greater than 𝑣0, but not necessarily twice as great.
4. It moves with a constantly increasing speed.
5. Its speed increases for a while, but then eventually reaches a constant speed.

1. A box of mass m is sitting on the floor of an elevator. The elevator is slowing down while moving upward.  The magnitude of the normal force on the box is

1. >
2. =
3. <
4. = 0.
5. none of the above, as not enough information is provided.

1. A box with a weight of 100 N is at rest. It is then pulled by a 30 N horizontal force.   How many forces are on the box?  Does the box move?

1. 3 forces. The box moves.
2. 4 forces. The box moves.
3. 5 forces. The box moves.
4. 5 forces. The box doesn’t move.
5. 4 forces. The box doesn’t move.

1. A tire 0.300 m in radius rotates at a constant rate of 200 rev/min. Find the speed and the period of a small stone lodged in the tread of the tire (on its outer edge).
2. 9 m/s; 3.33 s.
3. 9 m/s; 0.300 s
4. 28 m/s; 3.33 s.
5. 28 m/s; 0.300 s.
6. None of the above. (You must give the correct answer to get the credit.)

1. A 50 kg cart rolls down a 30° concrete incline. What is the cart’s acceleration if the coefficient of rolling friction is 0.10?

1. 00 m/s2
2. 98 m/s2
3. 05 m/s2
4. 75 m/s2
5. 92 m/s2

1. A particle is moving along the curse shown in the diagram below, does the velocity change direction? Is

at this instant?

 a) 2.6 N b) 3.6 N c) 5.9 N d) 4.3 N e) 4.9 N

1. The helicopter in the drawing is moving horizontally to the right at a constant velocity. The weight of the helicopter is W = 52100 N. The lift force L generated by the rotating blade makes an angle of 21.0° with respect to the vertical.  Determine the magnitude of the air resistance R that opposes the motion.

1. 48600 N
2. 20000 N
3. 18700 N
4. 13600 N
5. 40300 N

1. The top block of mass 5.0 kg is accelerated across a frictionless table by the falling mass m = 2.0 kg. The string is massless, and the pulley is both massless and frictionless.  The tension in the string is a)    49 N
2. 35 N
3. 28 N
4. 20 N
5. 14 N