# Midterm II Physics 231

1) A car starts to accelerate from rest with a=0.5 m/s2. What is its velocity after 100m?

a)2.5 m/s

b)5.0 m/s

c)10 m/s

d)20 m/s

e)unknown, because the mass of the car is not given

2) A canon is shot under an angle of 30.00 with respect to the ground with an initial velocity of 49.0 m/s. At what horizontal distance away from the cannon does the cannon ball reach its highest point?

a)50 m

b)106 m

c)212 m

d)245 m

e)none of the above

3) A mass of 7.0 kg lying on a slope (370 with respect to the ground) is connected via a string over a massless pulley to a second mass m2 (see drawing). Assuming that the slope is frictionless, what is the mass of m2 if the system remains stationary (i.e. the masses do not start to move when released)?

a)0.0 kg

b)2.0 kg

c)4.2 kg

d)5.6 kg

e)11.6 kg

4) Two vectors, one of length 4m and one of length 2m are added together but it is unknown what the relative angle between the two vectors is. What are the minimum and maximum magnitude of the resultant vector?

a)2m and 4m

b)2m and 6m

c)0.5m and 8m

d)3.5m and 4.5 m

e)0m and 6m

5) A block is launched up an incline plane. After going up, it slides back down to its starting position. The coefficient of kinetic friction between the block and the plane is 0.3. The speed of the block when it reaches the starting position on the trip down:

a)the same as the launching speed

b)is less than the launching speed

c)is more than the launching speed

d)cannot be compared to the launching speed with the information given

e)could be the same or more than the launching speed

6) Robert and Paul pull a crate of 50 kg as indicated in the figure. Robert pulls with a force of 80N and Paul with a force of 60N. What is the magnitude of the acceleration of the crate if the coefficient of kinetic friction is 0.10?

a)m/s2

b)1.8 m/s2

c)m/s2

d)2.8 m/s2

e)the crate doesn't accelerate at all

7) A grasshopper raises to a maximum height h in each jump. Consider the initial velocity is at 45 degrees. What is the initial speed of the grasshopper?

a);

b);

c);

d);

e)

(Hint: v0x=v0y sincesin°cos°=1/

8) Two object are connected by a light string passing over a light frictionless pulley. Object m1 is released from rest at a point 4.00 m above the floor. Determine the acceleration of the system

a)g

b)m1g/(m1+m2)

c)m2g/(m1+m2)

d)(m1-m2)g/(m1+m2)

e)(m1+m2)g/(m1-m2)

9) A bullet is fired with an initial speed v into a block that is initially at rest at the edge of a table of height 1.00 m. The bullet remains in the block, and after the impact the block flies off the table with a speed 0.20 m/s and eventually lands at a distance d from the bottom of the table. If the mass of the block of 50.0 g and the mass of the bullet is 1.00 g, what was the initial speed v of the bullet?

a)102 m/s

b)98.0 m/s

c)1.02 m/s

d)m/s

e)0.20 m/s

10) A 600 Kg satellite is in circular orbit around the Earth at a height equal to the Earths mean radius. What is the speed at which the satellite is orbiting? (G=6.67x10-11 Nm2, ME=5.98x1024 Kg, RE=6.38x106 m)

a)3.05 m/s

b)7.91 x103 m/s

c)5.59 x103 m/s

d)5.60x10-8 m/s

e)11.2x103 m/s

11) Aliens in planet X intend to launch a rocket. What is its escape speed from the unknown planet X, if the mass is 7.36x1022 Kg and radius R is 9.82x106 m?

a)x103 m/s

b)7.07 x103 m/s

c)2.00 x103 m/s

d)0.32 m/s

e)It cannot be calculated because the mass of the rocket is not given.

(Hint: for the escape velocity, the kinetic energy of the rocket will be just enough to overcome the potential energy of the rocket due to the gravitational energy.)

12) A hungry bear with weight W1=1000N walks out on a beam in an attempt to retrieve some "goodies" weighing W2=50 N hanging at the end as shown in the figure. The beam has length L=5 m, and its weight is assumed to be negligible. If the tension on the supporting string is T=350 N, how far is the bear along on the beam? That is, what is x?

a)0.5 m1.

b)0 m

c)1.5 m

d)2.0 m

e)3.0 m

13) Pure argone gas is admitted into a leak-proof cylinder containing a movable piston. The initial volume, pressure, and temperature of the gas are 15 L, 2.0 atm, and 300 °K. If the piston is moved so that the volume is decreased to 10 L and the pressure is increased to 4 atm, find the final temperature of the gas.

a)200 °K

b)300 °K

c)400 °K

d)500 °K

e)600 °K

14) A piece of rock is hung at the end of a string and dipped into a glass jar of water which is initially filled to the brim. 204 cm3 of water spills out. The apparent weight of the rock, as measured by a scale from which the other end of the string is hung, is 5 N. The actual weight of the rock is closest to:

a)5.98 N

b)6.51 N3

c)7.02 N

d)8.05 N

e)not enough information to decide
15) A frisbee flies through the air. It is shaped in such a way that the velocities of air flow above and below (relative to the frisbee) are va = 5 m/s and vb= 4 m/s respectively. What is the difference in pressure on the two sides (pb – pa)? Assume the air density is 1.3 kg/m3. (The slight difference in gravitational potential energy of the two sides can be ignored.)

a)not enough information to determine;

b)there is no pressure difference;

c)2.45 Pa

d)4.55 Pa

e)5.85 Pa

16) A solid cylinder of mass M and radius R (moment of inertia I=½MR2), rolls (without slipping) down an inclined plane of height h and angle . The linear velocity of the center of the cylinder at the base is found to be 4 m/s. The height h of the inclined plane is closest to:

a)1.22 m

b)1.62 m

c)0.61 m

d)0.85 m

e)not enough information since  is not given.

17) A student uses a 150W electric immersion heater to heat 0.2 kg of water from
20 °C to 100 °C to make tea. How long will it take?

a)1 min.

b)180 s

c)447 s

d)5 min.

e)123 s

18) A window has a glass surface of 0.160 m2 and a thickness of 3.00 mm. The thermal conductivity of the glass is 0.84 J/s m 0C. Determine the rate of energy transfer by conduction through this pane in the summer, when the temperature of the inside surface of the glass is 70 0 F and the outside temperature is 90 0 F is:

a)There is no thermal conduction through the window.

b)8.98 x103 J/s

c)896 J/s

d)4.98 x103 J/s

e)498 J/s

19) Consider the following PV diagrams. Note that the arrows on the diagrams represent the order in which the processes occur. Which of the following statements is correct:

a)The work performed to take the gas from the initial to the final state is the same in all cases.

b)The heat transferred to the gas is the same in all cases.

c)Diagram (c) can represent an isothermal process.

d)Diagram (b) consists of an isobaric process followed by an isovolumetric process.

e)Diagram (a) consists of an isothermal process followed by an adiabatic process.

20) In one cycle, a heat engine absorbs 500 J from the hot reservoir and expels 300 J to the cold reservoir. If it were a Carnot engine, what would be the ratio of the temperatures of the hot reservoir and the cold reservoir?

a)2/3

b)3/5

c)2/5

d)5/2

e)1/3

21) A pendulum clock that works well on Earth is taken to a different planet. Knowing that the clock in the unknown planet ticks at twice the speed, what can you conclude about the gravitational acceleration at the surface of this planet in terms of acceleration at the surface of Earth, g?

a)2g

b)4g

c)g/2

d)g

e)g/4

22) Thesnapshot (at one specific instant of time) of two waves, A and B, is represented in the figure. Which of the following statements is correct?

a)The amplitudes of the waves are the same.

b)The wavelength of A is twice the wavelength of B.

c)The period of oscillation of A is the same as that of B.

d)The speed of wave A is smaller than the speed of wave B

e)None of the above.

23) A long open pipe is 1.715 m long. Pressing the mouth against the pipe and blowing air into it, produces a sound that consists of the superposition of the several harmonics of the pipe. What are the frequencies of the first three harmonics? (the speed of the sound is v=343m/s)

a)100 Hz, 200 Hz, 300 Hz.

b)200 Hz, 400 Hz, 600 Hz.

c)100 Hz, 300 Hz, 500 Hz.

d)50 Hz, 100 Hz, 150 Hz.

e)50 Hz, 150 Hz, 250 Hz.

24) A train approaches a station at constant speed, blowing the whistle, with no intention to stop. A person standing on the platform notices that:

a)as the train approaches the frequency of the sound increases and the intensity decreases.

b)as the train approaches both the intensity and the frequency of the sound decreases.

c)as the train approaches the intensity of the sound decreases whilst the frequency remains constant.

d)as the train approaches both the intensity and the frequency remain constant.

e)as the train approaches both the intensity and the frequency increase.