PC1431 Term Test 2015

September 21, 2017 | Author: Ng Jia Cheng | Category: Acceleration, Mechanical Engineering, Mass, Quantity, Spacetime
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PC1431 Physics IE 2015 – 2016 Semester I TERM TEST 2nd October Time Allowed: ONE hour THIRTY minutes INSTRUCTIONS 1. 2. 3. 4.

5. 6. 7. 8. 9.

This is a closed book test. This paper contains 20 multiple choice questions. Answer all questions. Marks will NOT be deducted for wrong answers. Each of the questions or incomplete statements is followed by the suggested answers or completions. Select the one that is best in each case and then shade the corresponding bubble on the answer sheet. Only the answer sheet will be collected at the end of the test. Use 2B pencil only. Using any other type of pencil or pen may result in answers unrecognizable by the machine. Only nonprogrammable and non-graphing calculators are allowed. Take the acceleration due to gravity, 9.80 m⁄s . You may find the following mathematical formulae useful: 4 √ 0 2 1 1

Department of Physics, National University of Singapore





For a force to be conservative, when applied to a single test body, (a) it must have the same value at every point in space. (b) it must have the same direction at every point in space. (c) it must do no work if the body returns to its original position. (d) it must be parallel to the displacement of the body at all times. (e) it must do equal work for any same distance travelled by the body.


In a contest, two tractors pull two identical blocks of stone the same distance over identical surfaces. However, block A is moving twice as fast as block B when it crosses the finish line. Which statement is correct? (a) Block A has twice as much kinetic energy as block B. (b) Both blocks have had equal losses of energy to friction. (c) Block A has lost twice as much kinetic energy to friction as block B. (d) Block B has lost twice as much kinetic energy to friction as block A. (e) No energy is lost to friction because the ground has no displacement.


A ball of mass long.

0.275 kg swings in a vertical circular path on a string

0.850 m

Figure 1 ⁄ If its speed is 5.20 m s at the top of the circle, what is the tension in the string there? (a) 2.70 N (b) 6.05 N (c) 8.50 N (d) 8.75 N (e) 9.50 N 4.

A 70 kg athlete can produce one horsepower (i.e., 746 W) for a short period of time. The number of 16 cm high steps that he could ascend in one minute while expending one horsepower is approximately (a) 400 (b) 250 (c) 110 (d) 70 (e) 7

Department of Physics, National University of Singapore



A 2.0 kg object is dropped at time 0 s from the roof of a building of height 2.0 m. While the object is falling, a wind blowing parallel to the face of the building exerts a constant horizontal force 19.6 N on the object. How far is the object displaced horizontally before hitting the ground? (a) 0.50 m (b) 1.0 m (c) 1.5 m (d) 2.0 m (e) 2.5 m


A helicopter hovers in the sky. A parachutist who jumped from it is now drifting vertically downward at a constant 11.0 m⁄s. When the parachutist is 8.40 m directly below the aircraft, the pilot throws a ball straight downward at 2.20 m⁄s. Treating the ball as a freely falling body, what is the difference in the speeds of the ball and the parachutist when they meet? (a) 0.00 m⁄s. (b) 9.80 m⁄s. (c) 11.0 m⁄s. (d) 15.6 m⁄s. (e) 26.6 m⁄s.


Suppose a child whirls a stone in a horizontal circle 1.90 m above the ground by means of a string 1.40 m long. The string breaks, and the stone flies off horizontally, striking the ground 11.0 m away. What was the centripetal acceleration of the stone while in uniform circular motion? (a) 23 m⁄s (b) 123 m⁄s (c) 223 m⁄s (d) 323 m⁄s (e) 423 m⁄s


The distance between two telephone poles is 50.00 m. When a 1.000 kg bird lands on the stretchable telephone wire midway between the poles, the wire sags 0.2000 m. How much tension does the bird produce in the wire? Ignore the weight of the wire. (a) 1225 N (b) 100.0 N (c) 212.5 N (d) 425.0 N (e) 612.5 N


An object is set into motion on a circular path of radius by giving it a constant tangential acceleration . The time when the acceleration vector points at 45° to the direction of motion is given by ⁄ . (a) ⁄2 (b) . (c) 2 ⁄ . ⁄ (d) 2 . (e) 2 ⁄ .

Department of Physics, National University of Singapore


10. A small container of water is placed on a turntable inside a microwave oven, at a radius of 12.0 cm from the centre.



θ water


Figure 2 The turntable rotates steadily, turning one revolution in each 7.25 s. What angle the water surface make with the horizontal? (a) 0.026° (b) 0.263° (c) 0.527° (d) 0.013° (e) 1.054°


11. A particle starts from the origin at time 0 with an initial velocity of 5.00 m⁄s along the positive axis. If the acceleration is 3.00 m⁄s ̂ 4.50 m⁄s ̂, the distance of the particle from at the moment it reaches its maximum coordinate is approximately (a) 4.17 m. (b) 5.21 m. (c) 6.25 m. (d) 7.51 m. (e) 15.8 m. 12. A 1.00 kg block is resting against a light, compressed spring at the bottom of a rough plane inclined at an angle of 30.0°. The coefficient of kinetic friction between the block and the 0.100. Suppose the spring is compressed 10.0 cm from its equilibrium plane is length. The spring is then released, and the block separates from the spring and slides up the incline a distance of only 2.00 cm beyond the spring’s normal length before it stops. What is the spring constant k? (a) 100 N⁄m (b) 138 N⁄m (c) 215 N⁄m (d) 276 N⁄m (e) 690 N⁄m

Department of Physics, National University of Singapore


13. A truck is moving with constant acceleration horizontal.

up a hill that makes an angle

with the


φ Figure 3 A small sphere of mass is suspended from the ceiling of the truck by a light cord. If the pendulum makes a constant angle with the perpendicular to the ceiling, what is ? (a) cos tan (b) sin tan (c) sin tan cos (d) cos sin sin (e) cos tan sin 14. An object is fired from ground level, as shown in Figure 4.

Figure 4 Treating it as a projectile, its time of flight (a) 8 ⁄ . ⁄2 . (b) ⁄4 . (c) (d) 4 ⁄ . (e) 2 ⁄ .

Department of Physics, National University of Singapore

and maximum height

are related by


15. Assume all surfaces and the pulley are frictionless.

Figure 5 What horizontal force must be applied to the large block of mass , as shown in Figure and remain stationary relative to ? 5, so that the blocks of masses ⁄ (a) ⁄ (b) (c) ⁄ (d) ⁄ (e) 16. The potential energy of two atoms in a diatomic (two-atom) molecule can be written as , where is the distance between the two atoms and and are positive constants. At what value of would the force between the two atoms be zero? ⁄ (a) ⁄ ⁄ (b) (c) 2 ⁄ ⁄ (d) 5 ⁄11 ⁄ (e) Never. There is no position where the force is zero. 17. The position of a particle is given by 2.00 m⁄s 1.00 m⁄s 10.0 m. 3.00 m⁄s What is its acceleration at the instant when it is instantaneously at rest? (a) 9.90 m⁄s (b) 7.21 m⁄s (c) 2.00 m⁄s (d) 0.00 m⁄s (e) 1.44 m⁄s 18. The speed of a bullet as it travels down the barrel of a rifle toward the opening is given by 5.00 10 m⁄s 3.00 10 m⁄s , where time is in seconds and is in metres per second. Suppose at 0, the bullet is 0.00 m. Find the position of the bullet when its acceleration is zero. at (a) 0.900 m (b) 0.675 m (c) 1.80 m (d) 1.35 m (e) 1.13 m

Department of Physics, National University of Singapore


19. As a driver steps on the gas pedal, a car of mass 1160 kg accelerates from rest. During the first few seconds of motion, the car’s acceleration a increases with time according to 0.240 , 1.16 0.210 where is in seconds. What is the wheels’ output power at the instant 2.50 s? (a) 4.93 kW (b) 6.19 kW (c) 12.3 kW (d) 28.5 kW (e) 30.2 kW 20. A car moves into the page and is rounding a curve on a road banked at an angle to the horizontal. The radius of curvature of the road is , and the coefficient of static friction is .

Car θ Figure 6 About the range of the speed that the car can have without slipping up or down the road, which of the following is TRUE? (a) The range of is not constrained. (b) (c) (d) (e) – End of Paper –

Department of Physics, National University of Singapore

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