TMA1/PHY101

My TMA Home TMA Results My Pending TMA Quick Help TMA Quiz Questions TMA: TMA1/PHY101 : score=9.50 PHY101 - Elementary Mechanics, Heat and Properties of Matter Mr. Ibanga Efiong (eibanga@noun.edu.ng ) 1 A stationary observer at a railway station sees a passenger in a railway coach that is in motion at constant speed in a straight and horizontal track. Which of the following best describes the frames of reference from which both the observer and the passenger describe each other's motion? inertial uniform constant relativistic 2 Consider the two observers O and O′$$O^{{}^{\prime }}$$ at the origins of the frames of reference S$$S$$ and S′$$S^{{}^{\prime }}$$ respectively, which are in relative motion at constant velocity v$$v$$ along the x-axis as illustrated in figure TMA 1_Fig1. Suppose the origins O$$O$$ and O′$$O^{{}^{\prime }}$$ as well as the axes of the coordinates of these frames are coincident at an initial time t=t′=0$$t=t^{{}^{\prime }}=0$$ . The two observers are equipped with measuring instruments to determine the coordinates of the event at P. Measurements made in the S$$S$$ frame are related to those made in the S′$$S^{{}^{\prime }}$$ by the following EXCEPT Click here to see exhibit x′=x−vt$$x^{{}^{\prime }}=x-vt$$ y′=y$$y{}^{\prime }=y$$ t′=t$$t^{{}^{\prime }}=t$$ z′=z+vt$$z^{{}^{\prime }}=z+vt$$ 3 The joule (J) is the same as kgm−1s−2$$kg{m}^{-1}{s}^{-2}$$ kgm−2s−1$$kg{m}^{-2}{s}^{-1}$$ kgm2s−2$$kg{m}^2{s}^{-2}$$ kgms−1$$kgm{s}^{-1}$$ 4 The dimension of power is ML−2T2$$M{L}^{-2}{T}^2$$ ML2T−2$$M{L}^2{T}^{-2}$$ MLT−2$$ML{T}^{-2}$$ ML2T−3$$M{L}^2{T}^{-3}$$ 5 Which of the following physical quantities is an example of a cross product? work moment power momentum 6 Given two vectors a⃗ =4i^−3j^+2k^$$\overrightarrow{a}=4\hat{i}-3\hat{j}+2\hat{k}$$ , b⃗ =i^+2j^−k^$$\overrightarrow{b}=\hat{i}+2\hat{j}-\hat{k}$$ , calculate a⃗ ×b⃗ $$\overrightarrow{a}\times \overrightarrow{b}$$ 2^i−6j^−5k^$$\hat{2}i-6\hat{j}-5\hat{k}$$ −i^+6j^+5k^$$-\hat{i}+6\hat{j}+5\hat{k}$$ −i^−6j^+5k^$$-\hat{i}-6\hat{j}+5\hat{k}$$ −2^i−6j^+5k^$$-\hat{2}i-6\hat{j}+5\hat{k}$$ 7 A driver does a round trip to Ibadan from Lagos, returning to his take-off point in five hours. The distance of Ibadan from Lagos is 130 km. What is his average velocity? 52 km/h 26 km/h 0 km/h 104 km/h 8 An object is thrown upward from the edge of a tall building with a velocity of 20 m/s. Where will the object be 5 s after it is thrown? Take g=10ms−2$$g=10m{s}^{-2}$$ 25 m above the top of the building 22 m below the top of the building 25 m below the top of the building 22 m above the top of the building 9 A car accelerates from rest to a speed of 10 m/s in a time of 8 s. What is the acceleration and how far will it go in this time? 1.25ms−2$$1.25m{s}^{-2}$$ , 40 m 2.50ms−2$$2.50m{s}^{-2}$$ , 40 m 1.25ms−2$$1.25m{s}^{-2}$$ , 30 m 1.50ms−2$$1.50m{s}^{-2}$$ , 30 m 10 A cart is moving horizontally along a straight line with constant speed of 30 m/s. A projectile is fired from the moving cart in such a way that it will return to the cart after the cart has moved 80 m. At what speed (relative to the cart) and at what angle (to the horizontal) must the projectile be fired? 35.8 m/s at 24 degrees 38.6 m/s at 54 degrees 27.2 m/s at 35 degrees 24.3 m/s at 44 degrees 11 A projectile shot at an angle of 60 degrees above the horizontal strikes a wall 25 m away at a point 16 m above the level of projection. What is the magnitude of the velocity with which the projectile hits the wall? 25. 44 m/s 21.11 m/s 11.62 m/s 14.63 m/s 12 A 10-g bullet of unknown speed is shot horizontally into a 2-kg block of wood suspended from the ceiling by a cord. The bullet hits the block and becomes lodged in it. After the collision, the block and the bullet swing to a height 30cm above the original position. What was the speed of the bullet? (This device is called the ballistic pendulum). Take g=9.8ms−2$$g=9.8m{s}^{-2}$$ 700 m/s 640 m/s 354 m/s 487 m/s 13 A uniform plank AB 30 m long, weighing 100 N is pivoted at points P, Q which are 5 m from the ends A and B respectively. A boy of weight 250 N stands at a point D on the plank, 1 m away from Q and the arrangement is in equilibrium. Determine the reaction R1$$R_1$$ and R2$$R_2$$ at the supports. 77.5 N, 245.5 N 105.5 N 33.5 N 37.5 N, 312.5 N 27.5 N, 232.5 N 14 A force of 2i⃗ +7j⃗ $$2\overrightarrow{i}+7\overrightarrow{j}$$ N acts on a body of mass 5kg for 10 seconds. The body was initially moving with constant velocity of i⃗ −2j⃗ m/s$$\overrightarrow{i}-2\overrightarrow{j}m/s$$ . Find the final velocity of the body in m/s, in vector form. 5i⃗ +12j⃗ $$5\overrightarrow{i}+12\overrightarrow{j}$$ 12i⃗ −5j⃗ $$12\overrightarrow{i}-5\overrightarrow{j}$$ 10i⃗ −7j⃗ $$10\overrightarrow{i}-7\overrightarrow{j}$$ 7i⃗ +10j⃗ $$7\overrightarrow{i}+10\overrightarrow{j}$$ 15 The exhaust gas of a rocket is expelled at the rate of 1300 kg/s, at the velocity of 50 000 m/s. Find the thrust on the rocket in newtons 6.5×107$$6.5\times {10}^7$$ 3.5×107$$3.5\times {10}^7$$ 7.6×107$$7.6\times {10}^7$$ 5.7×107$$5.7\times {10}^7$$ 16 Sand drops at the rate of 2000 kg/min. from the bottom of a hopper onto a belt conveyor moving horizontally at 250 m/min. Determine the force needed to drive the conveyor, neglecting friction. 500 N 800 N 139 N 152 N 17 How large an average force is required to stop a 1400-kg car in 5.0 s if the car’s initial speed is 25 m/s? 2000 N 3500 N  9000 N  7 000N 18 Which of these is NOT a statement of Newton’s law of universal gravitation? gravitational force between two particles is attractive as well as repulsive  gravitational force acts along the line joining the two particles  gravitational force is directly proportional to the product of the masses of the particles  gravitational force is inversely proportional to the square of the distance of the particles apart 19 What is the gravitational field strength at a height h above the surface of the Earth? R is the radius of the earth gR2(R+h)2$$\frac{g{R}^2}{(R+h{)}^2}$$ gR(R+h)$$\frac{gR}{(R+h)}$$ g(R−h)R$$\frac{g(R-h)}{R}$$ g(R−h)2R2$$\frac{g(R-h{)}^2}{R^2}$$ 20 A 2000 kg satellite orbits the earth at a height of 300 km. What is the speed of the satellite and its period? Take G=6.67×10−11Nm2/kg2$$G=6.67\times {10}^{-11}N{m}^2/k{g}^2$$ , Mass of the earth is 5.98×1024$$5.98\times {10}^{24}$$ kg 7.73 km/s and 5.4×103$$5.4\times {10}^3$$ s 855.4km/s and 7.7×104$$7.7\times {10}^4$$ s 497.2km/s and 5.5×105$$5.5\times {10}^5$$ s 322.3km/s and 4.3×104$$4.3\times {10}^4$$ s