dubemjerry Posts: 1, Reputation: 1 New Member #1 Nov 11, 2011, 02:24 AM
elementry mechanics
please I need help urgently

( 1.) 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?<
The passenger is in motion relative to the passer-by
The passer-by is stationery 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)

( 5.) Two forces act on a point object as follows: 100N at 170derees and 100N at 50degrees. Find their resultant force
( 6.) Given three vectors a = -i-4j 2k, b = 3i 2j-2k, c = 2i-3j k, calculate a.(bxc)

( 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 40degrees. Calculate the magnitude of B

( 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 returnes home to his garrage two hours after. What is his average velocity from home in Km/h?
( 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 benaeth the tree. How far behind him in metres does the coconut hit the ground?

( 10.) 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 benaeth the tree actually intending to hit the toes of the zoo keeper, how early in seconds should the coconut be dropped by the monkey to achieve his aim?

( 11.) Which of the following statements is correct?
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?

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

( 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 newtons are

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

( 16.) Which of the following does not contribute to the determination 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 tension T in the upper part of the first rope
27.2N and 39.2N
40.5N and 62.5N
30.4N and 53.7N
16.6N and 27.3N

________________________________________
( 18.) 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?
28.7N
54.3N
37.6N
63.4N

________________________________________
( 19.) A body hangs from a spring balance supported from the roof of an elavator. If the elavator has an upward acceleration of 3m/s2 and the balance reads 50N, what is the true weight of the body?

( 1.) An objectis thrown upward from the edge of a tall building with a velocity of 10m/s. Where will the object be 3s after it is thrown? Take g = 10m/s^2

( 2.) A stone thrown from ground level returns to the same level 4s after. With what speed was the stone thrown? Take g = 10m/s^2
( 3.) What is common to the variation in the range and the height of a projectile?

( 4.) A cart is moving horizontally along a straight line with constant speed of 30m/s. A projectile is fired from the moving cart in such a way that it it will return to the cart after the cart has moved 80m. At what speed (relative to the cart) and at what angle (to the horizontal) must the projectile be fired?

( 5.) The trajectory of a projectile is

( 6.) How fast must a ball be rolled along the surface of a 70-cm high table so that when it rolls off the edge it will strike the floor at the same distance (70cm) from the point directly below the edge of the table?

( 7.) A ball is kicked and flies from point P to Q following a parabolic path in which the highest point reached is T. The acceleration of the ball is

( 8.) A mass accelerates uniformly when the resultant force acting on it

( 9.) The term that best describes the need to hold the butt of a riffle firmly against the shoulder when firing to minimise impact on the shoulder is

( 10.) Two trolleys X and Y with momenta 20 Ns and 12 Ns respectively travel along a straight line in opposite directions before collision. After collision the directions of motion of both trolleys are reversed and the magnitude of the momentum of X is 2 Ns. What is the magnitude of the corresponding momentum of Y?

( 11.) A force of 2i 7j N acts on a body of mass 5kg for 10 seconds. The body was initially moving with constant velocity of I – 2j m/s. Find the velocity of the body in m/s, in vector form.

( 12.) The exhaust gas of a rocket is expelled at the rate of 1300kg/s, at the velocity of 50,000m/s. Find the thrust on the rocket in newtons

( 13.) Sand drops at the rate of 2000kg/min. from the bottom of a hopper onto a belt conveyor moving horizontally at 250m/min. Determine the force needed to drive the conveyor, neglecting friction.

( 14.) A 30,000-kg truck travelling at 10.0m/s collides with a 1700-kg car travelling at 25m/s in the opposite direction. If they stick together after the collision, how fast and in what direction will they be moving?

( 15.) A gun of mass M is used to fire a bullet of mass m. The exit velocity of the bullet is v. Find the recoil velocity of the gun
( 16.) A 40-g ball travelling to the right at 30cm/s collides head on with an 80-g ball that is at rest. If the collision is perfectly elastic, find the velocity of each ball after collision

the first ball is going to the right at 10m/s while the other is going to the left at 10m/s
( 17.) A 10-g pellet of unknown speed is shot into a 2000-kg block of wood suspended from the ceiling by a cord. The pellet hits the block and becomes lodged in it. After the collision, the block and the pellet swing to a height 30cm above the original position. What was the speed of the pellet? (This device is called the ballistic pendulum)
( 18.) How large an average force is required to stop a 1400-kg car in 5.0s if the car's initial speed is 25m/s

( 19.) Which of these is not a statement of Newton's law of universal gravitation?

( 20.) What is the gravitational field strength at a height h above the surface of the Earth?
 ebaines Posts: 12,132, Reputation: 1307 Expert #2 Nov 11, 2011, 12:28 PM
We aren't going to solve all these for you - sorry. Make the effort to show us what you think the answers are, and why, and we'll check them for you.
 okoyejob Posts: 1, Reputation: 1 New Member #3 Apr 26, 2012, 05:05 AM
1.d
2.a
3.ML^2T-^3
5.100N at 110 degree
6.-6
7.14.8
8.20
9.2.25
10.3.02
11.d
12.150
13.a
14.25.0 and 43.3
15.inertia
16.central equilibrium
17.16.2N and 27.3N
18.28.7N
19.50.0N
this is my answers to the first question from 1 to 19.please I need your correction.

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