COMPLETE QUESTION AND ANSWER TO PHY101: Elementary Mechanics, Heat &properties Of Matter TMA1

Question 1 : Given three vectors $\vec{a}=-\vec{i}-4\vec{j}+2\vec{k}$, $\vec{b}=3\vec{i}+2\vec{j}-2\vec{k}$, $\vec{c}=2\vec{i}-3\vec{j}+\vec{k}$, calculate $\vec{a}\cdot (\vec{b}\times \vec{c})$

 6

 9

 $-6$

 $-9$

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Question 2 : A boy intends to move an m-kg crate across the floor by applying a constant force P newtons on it.The coeficient of friction between the floor and the crate is $\mu$. Which of these is the best option for his task?

 Pull the crate with P inclined at an angle above the horizontal

 Push the crate with P inclined at an angle above the horizontal

 Pull the crate with P inclined an angle below the horizontal

 Pull the crate with P applied horizontally

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Question 3 : A stone thrown from ground level returns to the same level 4 s after. With what speed was the stone thrown? Take $g=10m{s}^{-2}$

 15 m/s

 10 m/s

 20 m/s

 30 m/s

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Question 4 : A rope suspended from a ceiling supports an object of weight W at its opposite end. Another rope tied to the first at the middle is pulled horizontally with a force of 30N. The junction P of the ropes is in equilibrium. Calculate the weight W and the tension T in the upper part of the first rope

 30.4N and 53.7N

 40.5N and 62.5N

 16.6N and 27.3N

 27.2N and 39.2N

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Question 5 : What are the dimensions of power (time rate of change of expending energy)

 $ML{T}^{-2}$

 $M{L}^2{T}^{-3}$

 $M^2{L}^2{T}^{-3}$

 $M{L}^2{T}^{-2}$

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Question 6 : What is common to the variation in the range and the height of a projectile?

 horizontal velocity

 time of flight vertical velocity, horizontal acceleration

 vertical velocity

 horizontal acceleration

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Question 7 : The speed of 90 hm/hr is equal to —————— m/s

 150

 324

 90

 25

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Question 8 : Which of the following contributes to the instability of an object?

 broad base of the object

 low potential energy

 low centre of gravity

 high centre of gravity

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Question 9 : A passenger in a moving car and a passerby standing at the road side see each other as moving in the opposite direction. Which of the following is NOT true?

 Both observers are in motion relative to each other

 The passer-by is stationary relative to the passenger

 The passenger is in motion relative to the passer-by

 The passer-by is in motion relative to the passenger

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Question 10 : The resultant of vectors $\vec{A}$ and $\vec{B}$ has a magnitude of 20 units.$\vec{A}$ has a magnitude of 8 units, and the angle between $\vec{A}$ and $\vec{B}$ is ${40}^o$. Calculate the magnitude of $\vec{B}$

 14.8

 12.6

 16.2

 18.4

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Question 11 : Which of the following does NOT refer to the terms description of stability of on an object?

 unstable equilibrium

 neutral equilibrium

 central equilibrium

 stable equilibrium

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Question 12 : A body hangs from a spring balance supported from the roof of an elavator. If the elavator has an upward acceleration of $3m{s}^{-2}$ and the balance reads 50 N, what is the true weight of the body?

 50.0 N

 28.3 N

 39.8 N

 38.3 N

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Question 13 : Which of the following physical concepts best explains why passengers in fast moving cars should always fasten their seat-belts?

 moment

 centripetal force

 terminal velocity

 inertia

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Question 14 : An object is thrown upward from the edge of a tall building with a velocity of 10 m/s. Where will the object be 3 s after it is thrown? Take $g=10m{s}^{-2}$

 15 m above the top of the building

 30 m above the building

 15 m below the top of the building

 30 m below the top of the building

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Question 15 : Which of the following statements is not correct about reference frames?

 Laws of physics are invariant (retain the same form) in inertial reference frames

 Any reference frame moving at constant velocity with respect to an inerial reference frame is also inertial

 If the coordinate axes of a reference frame attached to an object remain fixed in space then the object is at rest

 In non-inertial reference frames the motion of objects depend only on the interactions of constituent particles among themselves

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Question 16 : Two forces act on a point object as follows: 100 N at ${170}^o$ and 100N at ${50}^o$. Find the resultant force

 100 N at ${110}^o$

 110 N at ${100}^o$

 100 N at ${50}^o$

 110 N at ${50}^o$

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Question 17 : 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?

 27 m/s at 35 degrees

 35.8 m/s at 24 degrees

 38.6 m/s at 54 degrees

 24 m/s at 44 degrees

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Question 18 : The trajectory of a projectile is

 a parabola

 a straight line

 a circle

 an ellipse

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Question 19 : A man leaves the garrage in his house and drives to a neighbouring town which is twenty kilometres away from his house on sight-seeing. He returns home to his garrage two hours after. What is his average velocity from home in km/h?

 10

 20

 40

 0

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Question 20 : A 50kg boy suspends himself from a point on a rope tied horizontally between two vertical poles. The two segments of the rope are then inclined at angles 30 degrees and 60 degrees respectively to the horizontal.The tensions in the segments of the rope in newtons are

 50.0 and 25.0

 100.0 and 43.5

 25.0 and 43.3

 100.0 and 25.0

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