Revision Questions in Physics 101Dr. Aladdin Abdul-Latif

Physics Department

2The length of a spring increases by 7.2 cm from its relaxed length when a mass of 1.4 kg is suspended from the spring. (a) What is the spring constant? (b) A different mass is suspended and the spring length increases by 12.2 cm from its relaxed length. What is the second mass?

A) (a) 2.8 N/cm; (b) 2.0 kg

B) (a) 0.7 N/cm; (b) 2.0 kg

C) (a) 1.9 N/cm; (b) 3.0 kg

D) (a) 1.9 N/cm; (b) 2.4 kg

E) (a) 2.8 N/cm; (b) 2.4 kg

3A 4.0-kg object is lifted 1.5 m. (a) How much work is done against the Earth's gravity? (b) Repeat if the object is lowered instead of lifted.

A) (a) 59 J, (b) -59 J

B) (a) 6 J, (b) -6 J

C) (a) -59 J, (b) 59 J

D) (a) 39 J, (b) -39 J

4A proton (m=1.67 x 10-27 kg) that has a speed of 5.0 x 106 m/s passes through a metal film of thickness 0.010 mm and emerges with a speed of 2.0 x 106 m/s. How large an average force opposed its motion through the film?

A) 1.8 x 10-9 N

B) 7.5 x 10-10 N

C) 3.3 x 10-10 N

D) 3.5 x 10-12 N

5A 200-kg cart is pushed slowly up an incline. How much work does the pushing force do in moving the cart up to a platform 1.5 m above the starting point of friction is negligible?

A) 1.96 kJ

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B) 2.94 kJ

C) 0.30 kJ

D) 4.41 kJ

6Just before striking the ground, a 2.0-kg mass has 400 J of KE. If friction can be ignored, from what height was it dropped?

A) 200 m

B) 20 m

C) 40.8 m

D) 40.0 m

7At sea level a nitrogen molecule in the air has an average translational KE of 6.2 x 10-21J. Its mass is 4.7 x 10-26 kg. (a) If the molecule could shoot straight up without striking other air molecules, how high would it rise? (b) What is the molecule's initial speed?

A) (a) 14 km, (b) 0.51 km/s

B) (a) 1.35 x 1046, (b) 2.64 x 105

C) (a) 132 km, (b) 0.36 km/s

D) (a) 7.9 x 10-7, (b) 0.26 km/s

8A bead slides on a wire. Let A and B be two different points on the wire such that point A is a height h higher than point B. How large must height h1 be if the bead, starting at rest at A, is to have a speed of 200 cm/s at point B? Ignore friction.

A) 10.2 cm

B) 20.4 cm

C) 40.8 cm

D) 78.4 cm

9Compute the power output of a machine that lifts a 500-kg crate through a height of 20.0 m in a time of 60.0 s.

A) 1.63 KW

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B) 0.082 kW

C) 98 kW

D) 0.167 kW

10A 1000-kg auto travels up a 3.0 percent grade at 20 m/s. Find the horsepower required, neglecting friction.

A) 5880 hp

B) 263 hp

C) 7.9 hp

D) 4.4 x 106 hp

11A barge of mass 5.0 × 104 kg is pulled along the Erie Canal by two mules, walking along towpaths parallel to the canal on either side of it. The ropes harnessed to the mules make angles of 45° to the canal. Each mule is pulling on its rope with a force of 1.0 kN. How much work is done on the barge by both of these mules together as they pull the barge 150 m along the canal?

A) 350 kJ

B) 210 kJ

C) 150 kJ

D) 110 kJ

12Sam pushes a 10.0-kg sack of bread flour on a frictionless horizontal surface with a constant horizontal force of 2.0 N starting from rest. (a) What is the kinetic energy of the sack after Sam has pushed it a distance of 35 cm? (b) What is the speed of the sack after Sam has pushed it a distance of 35 cm?

A) (a) 0.70 J; (b) 0.37 m/s

B) (a) 7.0 J; (b) 0.37 m/s

C) (a) 0.70 J; (b) 0.21 m/s

D) (a) 7.0 J; (b) 3.5 m/s

E) (a) 3.5 J; (b) 3.5 m/s

13Typically, a tennis ball hit during a serve travels away at about 51 m/s. If the ball is at rest mid-air when struck, and it has a mass of 0.058 kg, what is the change in its momentum on leaving the racket?

A) 3000 kg·m/s

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B) 880 kg·m/s

C) 3.0 kg·m/s

D) 29 kg·m/s

14A 40,000-kg freight car is coasting at a speed of 5.0 m/s along a straight track when it strikes a 30,000-kg stationary freight car and couples to it. What will be their combined speed after impact?

A) 6.7 m/s

B) 2.9 m/s

C) 2.1 m/s

D) 5.0 m/s

15A 1200-kg gun mounted on wheels shoots an 8.00-kg projectile with a muzzle velocity of 600 m/s at an angle of 30.0°; above the horizontal. Find the horizontal recoil speed of the gun.

A) 4.00 m/s

B) 2.00 m/s

C) 3.46 m/s

D) 600 m/s

16A 2.0-kg block of wood rests on a tabletop. A 7.0-g bullet is shot straight up through a hole in the table beneath the block. The bullet lodges in the block, and the block flies 25 cm above the tabletop. How fast was the bullet going initially?

A) 6.3 km/s

B) 0.63 km/s

C) 2.2 km/s

D) 1.4 km/s

17During a soccer game a ball (of mass 0.425 kg), which is initially at rest, is kicked by one of the players. The ball moves off at a speed of 26 m/s. Given that the impact lasted for 8.0 ms, what was the average force exerted on the ball?

A) 1.4 kN

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B) 0.088 N

C) 13.7 kN

D) 1.38 N

18(a) What minimum thrust must the engines of a 2.0 x 105 kg rocket have if the rocket is to be able to rise from the Earth when aimed straight upward? (b) If the engines eject fuel at the rate of 20 kg/s, how fast must the gaseous fuel be moving as it leaves the engines? Neglect the small change in the mass of the rocket due to the ejected fuel.

A) (a) 20 N (b) 10 km/s

B) (a) 20 x 105 N (b) 98 km/s

C) (a) 20 x 103 N (b) 4.0 x 104 km/s

D) (a) 20 x 104 N (b) 1.0 x 10-8 km/s

19Two bodies of masses 8 kg and 4 kg move along the x-axis in opposite directions with velocities of 11 m/s in the positive x-direction and 7 m/s in the negative x-direction, respectively. They collide and stick together. Find their velocity just after collision.

A) 5.0 m/s - POSITIVE X-DIRECTION

B) 9.7 m/s - POSITIVE X-DIRECTION

C) 5.0 m/s - NEGATIVE X-DIRECTION

D) 7.5 m/s - POSITIVE X-DIRECTION

20A 2.0-kg block of wood rests on a long tabletop. A 5.0-g bullet moving horizontally with a speed of 150 m/s is shot into the block and sticks in it. The block then slides 270 cm along the table and stops. (a) Find the speed of the block just after impact. (b) Find the friction force between block and table.

A) (a) 370 m/s, (b) 0.00052 N

B) (a) 150 m/s, (b) 22.6 kN

C) (a) 0.37 m/s, (b) 0.052 N

D) (a) 3000 m/s, (b) 0.14 N

21A 6000-kg truck traveling north at 5.0 m/s collides with a 4000-kg truck moving west at 15 m/s. If the two trucks remain locked together after impact, with what speed and in what direction do they move immediately after the collision?

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A) 15.8 m/s at 18° north of west

B) 6.7 m/s at 27° north of west

C) 6.7 m/s at 63° north of west

D) 9.0 m/s at 27° north of west

22A 90-g ball moving at 100 cm/s collides head-on with a stationary 10-g ball. Determine the speed of each after impact if (a) they stick together, (b) the collision is perfectly elastic

A) (a) 90 cm/s, (b) 80 cm/s; 1.8 m/s

B) (a) 100 cm/s, (b) 80 cm/s; 20 cm/s

C) (a) 900 cm/s, (b) 90 cm/s; 90 cm/s

D) (a) 50 cm/s, (b) 1110 cm/s; 180 cm/s

23Two identical balls traveling parallel to the x-axis have speeds of 30 cm/s and are oppositely directed. They collide perfectly elastically. After collision, one ball is moving at an angle of 30°; above the +x-axis. Find its speed and the velocity of the other ball.

A) 30 cm/s, 30 cm/s at 60° below the -x-axis (opposite to the first ball)

B) 15 cm/s, 15 cm/s at 30° above the -x-axis (opposite to the first ball)

C) 30 cm/s, 30 cm/s at 30° below the -x-axis (opposite to the first ball)

D) 30 cm/s, 30 cm/s at 30° along the -x-axis (opposite to the first ball)

24Two balls of equal mass, moving with speeds of 3 m/s, collide head-on. Find the speed of each after impact if (a) they stick together, (b) the collision is perfectly elastic.

A) (a) 3 m/s, (b) 0 m/s

B) (a) 6 m/s, (b) 6 m/s

C) (a) 0 m/s, (b) each rebounds at 3 m/s

D) (a) 1.5 m/s, (b) 1.5 m/s

25A force of 200 N acts tangentially on the rim of a wheel 25 cm in radius. (a) Find the torque. (b) Repeat if the force makes an angle of 40°; to a spoke of the wheel.

A) (a) 50 N·m (b) 32 N·m

B) (a) 5000 N·m (b) 38 N·m

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C) (a) 8.0 N·m (b) 50 N·m

D) (a) 314 N·m (b) 3200 N·m

26A neutron star is formed when an object such as our Sun collapses. Suppose a uniform spherical star of mass M and radius R collapses to a uniform sphere of radius 10-5R. If the original star has a rotation rate of 1 rev each 25 days (as does the Sun), what will be the rotation rate of the neutron star?

A) 4.6 x 103 rev/s

B) 1.7 x 107 rev/s

C) 1.2 x 105 rev/s

D) 5.0 x 10-2 rev/s

27A large horizontal disk is rotating on a vertical axis through its center; for the disk, I=4000 kg m2. The disk is coasting at a rate of 0.150 rev/s when a 90.0-kg person drops onto the disk from an overhanging tree limb. The person lands and remains at a distance of 3.00 m from the axis of rotation. What will be the rate of rotation after the person has landed?

A) 0.125 rev/s

B) 0.141 rev/s

C) 5.5 rev/s

D) 0.137 rev/s

28A 500-g wheel that has a moment of inertia of 0.015 kg · m2 is initially turning at 30 rev/s. It coasts to rest after 163 rev. How large is the torque that slowed it?

A) 0.04 N·m

B) 0.26 N·m

C) 0.09 N·m

D) 4.50 N·m

29A 20-kg solid disk (I= 1/2Mr2) rolls on a horizontal surface at the rate of 4.0 m/s. Compute its total KE.

A) 80 J

B) 240 J

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C) 160 J

D) 320 J

30A wheel and axle having a total moment of inertia of 0.0020 kg · m2 is caused to rotate about a horizontal axis by means of an 800-g mass attached to a cord wrapped around the axle. The radius of the axle is 2.0 cm. Starting from rest, how far must the mass fall to give the wheel a rotational rate of 3.0 rev/s?

A) 5.3 cm

B) 4.5 cm

C) 52 cm

D) 3.8 cm

31A certain coin and a wedding ring have exactly the same mass and radius. When placed at the top of an incline, which object reaches the bottom of the incline first?

A) the coin

B) the wedding ring

C) the two objects reach the bottom at the same time

D) we cannot answer this question with the given information

32An ice skater is in a fast spin with her arms held tightly to her body. When she extends her arms, which of the following statements is not true?

A) She increases her moment of inertia.

B) She decreases her angular speed.

C) Her moment of inertia remains constant.

D) Her total angular momentum remains constant.

33The torque exerted on the moon by the gravitational pull of the earth is

A) normal to the direction of the moon's path.

B) parallel to the direction of the moon's path.

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C) tangent to the imaginary line connecting the earth and the moon.

D) zero.

34A turntable rotates through 10 radians in 4 seconds. The turntable experiences uniform acceleration. If the turntable started from rest, what is its angular velocity at the end of the 4 seconds?

A) 2.5 rad/s

B) 5 rad/s

C) 40 rad/s

D) we cannot calculate the answer since the angular acceleration was not given.

35The speed of glycerin flowing in a 5.0 cm i.d. pipe is 0.54 m/s. Find the fluid's speed in a 3.0 cm i.d. pipe that connects with it, both pipes flowing full.

A) 1.5 m/s

B) 0.9 m/s

C) 0.19 m/s

D) 0.32 m/s

36A large open tank of nonviscous liquid springs a leak 4.5 m below the top of the liquid. What is the theoretical velocity of outflow from the hole? If the area of the hole is 0.25 cm2, how much liquid would escape in exactly 1 minute?

A) (a) 9.4 m/s, (b) 0.0141 m3

B) (a) 88.3 m/s, (b) 0.000235 m3

C) (a) 3.0 m/s, (b) 2540 m3

D) (a) 4.7 m/s, (b) .846 m3

37A pipe of varying inner diameter carries water. At point 1 the diameter is 20 cm and the pressure is 130 kPa. At point 2, which is 4.0 m higher than point 1, the diameter is 30 cm. If the flow is 0.080 m3/s, what is the pressure at the second point?

A) 93 kPa

B) 91 kPa

C) 133 kPa

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D) 39 kPa

38A container is filled with gas at a pressure of 4.0 x 105 Pa. The container is a cube, 0.10 m on a side, with one side facing south. What is the magnitude and direction of the force on the south side of the container due to the gas inside?

A) 2.0 kN southward

B) 4.0 kN northward

C) 2.0 kN northward

D) 4.0 kN southward

39A certain town receives its water directly from a water tower. If the top of the water in the tower is 26.0 m above the water faucet in a house, what should the gauge pressure of the water at the faucet be? (Neglect the effects of other water users.)

A) 0.255 kPa

B) 255 kPa

C) 2.65 kPa

D) 127 kPa

40At a height of 10 km (33000 ft) above sea level, atmospheric pressure is about 210 mm of mercury. What is the resultant normal force on a 600 cm2 window of an airplane flying at this height? Assume the pressure inside the plane is 760 mm of mercury. The density of mercury is 13 600 kg/m3.

A) 6.1 kN

B) 4.4 x 104 kN

C) 1.2 x 103 kN

D) 4.4 kN

41A glass tube is bent into the form of a U. A 50.0 cm height of olive oil in one arm is found to balance 46.0 cm of water in the other. What is the density of the olive oil?

A) 920 kg/m3

B) 1090 kg/m3

C) 230 kg/m3

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D) 0.920 kg/m3

42On a day when the pressure of the atmosphere is 1.000 x 105 Pa, a chemist distills a liquid under slightly reduced pressure. The pressure within the distillation chamber is read by an oil-filled manometer (density of oil = 0.78 g/cm3). The difference in heights on the two sides of the manometer is 27 cm. What is the pressure in the distillation chamber?

A) 98 kPa

B) 2.1 kPa

C) 1.021 x 105 Pa

D) 211 Pa

43A metal cube, 2.00 cm on each side, has a density of 6600 kg/m3. Find its apparent mass when it is totally submerged in water.

A) 0.439 g

B) 8.01 g

C) 11.2 g

D) 44.8 g

44A solid piece of aluminum (=2.70 g/cm3) has a mass of 8.35 g when measured in air. If it is hung from a thread and submerged in a vat of oil (=0.75 g/cm3), what will be the tension in the thread?

A) 0.059 N

B) 0.082 N

C) 0.023 N

D) 0.105 N

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