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July 4, 2015

July 4, 2015

Posted by **mike** on Monday, April 23, 2012 at 8:00am.

The passenger is in motion relative to the passer-by

The passer-by is stationary relative to the passenger

Both observers are in motion relative to each other

The passer-by is in motion relative to the passenger

2 Which of the following statements is not correct about reference frames?

Laws of physics are invariant in inertial reference frames

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

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

3 What are the dimensions of power (time rate of change of expending energy)

MLT−2

ML2T−3

ML2T−2

M2L2T−3

4 The speed of 90 hm/hr is equal to ------------------ m/s

25

90

150

324

5 Two forces act on a point object as follows: 100 N at 170o and 100N at 50o. Find the resultant force

110 N at 50o

110 N at 100o

100 N at 110o

100 N at 50o

6 Given three vectors a=−i−4j+2k, b=3i+2j−2k, c=2i−3j+k, calculate a(bc)

−6

6

9

−9

7 The resultant of vectors A and B has a magnitude of 20 units.A has a magnitude of 8 units, and the angle between A and B is 40o. Calculate the magnitude of B

12.6

16.2

14.8

18.4

8 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

0

20

40

9 A monkey in a perch 20m high in a tree drops a coconut above the head of a zoo keeper as he runs with a speed 1.5m/s beneath the tree. How far behind him in metres does the coconut hit the ground?

2.25

3.06

2.02

3.03

10 A monkey in a perch 20 m high in a tree drops a coconut above the head of a zoo keeper as he runs with a speed 1.5 m/s beneath the tree actually intending to hit the toes of the zoo keeper, how early in seconds should the coconut be dropped by the monkey

1.50

2.04

1.35

3.02

11 Which of the follwing statements is correcct?

An object can have a constant velocity even though its speed is changing

An object can have a constant speed even though its velocty is changing

An object can have zero acceleration and eventually reverses its direction

An object can have constant velocity even though its acceleration is not zero

12 A boat propelled so as to travel with a speed of 0.50m/s in still water, moves directly (in a straight line) across a river that is 60m wide. The river flows with a speed of 0.30m/s. How long in seconds does it take the boat to cross the river?

36

120

150

200

13 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 . Which of these is the best option for his task?

Pull the crate with P applied horizontally

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

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

Pull the crate with P inclined an angle below the horizontal

14 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

25.0 and 43.3

50.0 and 25.0

100.0 and 43.5

100.0 and 25.0

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

moment

terminal velocity

inertia

centripetal force

16 Which of the following does NOT refer to the terms description of stability of on an object?

unstable equilibrium

stable equilibrium

neutral equilibrium

central equilibrium

17 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 tens

27.2N and 39.2N

40.5N and 62.5N

30.4N and 53.7N

16.6N and 27.3N

18 Which of the following contributes to the instability of an object?

low centre of gravity

broad base of the object

low potential energy

high centre of gravity

19 A 150-kg ladder leans against a smooth wall, making an angle of 30 degrees with the floor. The centre of gravity of the ladder is one-third the way up from the bottom. How large a horizontal force must the floor provide if the ladder is not to slip?

28.7 N

54.3 N

37.6 N

63.4 N

20 A body hangs from a spring balance supported from the roof of an elavator. If the elavator has an upward acceleration of 3ms−2 and the balance reads 50 N, what is the true weight of the body?

50.0 N

28.3 N

38.3 N

39.8 N

- physic -
**Henry**, Tuesday, April 24, 2012 at 9:50pm1. Both are in motion relative to each other. False.

4. 90km/h = 90,000m/3600s = 25 m/s.

5. 100N@170Deg. + 100N@50Deg.

X = 100*cos170+100*cos50 = -34.2 N.

Y = 100*sin170+100*sin50 = 93.97 N.

tanA = Y/X = 91.97/-34.2 = -2.74764.

A = -70Deg.,Cw = -70+180=110 Deg.,CCW.

Fr = X/cosA = -34.2 / cos110 = 100 N @

110 Deg.

8. d = V*t = 2*20 = 40 km.

V*2 = 40.

V = 40 / 2 = 20 km/h.

9. d = 4.9t^2 = 20 m.

4.9t*2 = 20.

t^2 = 20 / 4.9 = 4.08 s.

Tf = 2.02 S. = Fall time.

d = V*t = 1.5m/s * 2.02s = 3.03 m. =

dist. covered by runner.

- physic -
**Anonymous**, Saturday, November 2, 2013 at 7:08am1 C

2 B

3 B

4 A

5 C

6 B

7 D

8 C

9 D

10 D

11 C

12 B

13 C

14 A

15 C

16 D

17 C

18 A

19 B

20 A