PHYS 2211K Lecture Notes - Lecture 2: Ruili

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erinhound851

25 Aug 2016

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Average velocity: the rate of change of position. It is the ratio of the displacement of an object over the change in time. Velocity vectors: these vectors point in the same direction as the displacement vectors (previously mentioned last lecture/notes). The length of the average velocity is proportionate to the magnitude of the displacement vector from the initial to final position. The length of a velocity vector represents the speed of the object within two points; if the object had a constant velocity, then the points would be equidistant. Because velocity is a vector it can change in two ways: The average acceleration is the ratio of the change in velocity over the change in time. Acceleration in everyday life is used to describe an object that is speeding up, while decelerating is used for an object slowing down. In physics, accelerating is used for both slowing down and speeding up. Accelerating is used to describe the change in velocity.

Related Questions

1. What is the difference between speed and velocity?

a. Speed is an average quantity while velocity is not.

b. Velocity contains information about the direction of motion while speed does not.

c. Speed is measured in mph, while velocity is measure in m/s.

d. The concept of speed applies only to objects that are neither. speeding up or slowing down, while velocity applies to every kind of motion.

e. Speed is used to measure how fast an object is moving in a straight line, while velocity is used for objects moving along curved paths.

2. The quantity 2.67 x 10³ has how many significant figures?

3. If Libby walks 100 m to the right, then 200 m to the left, her net displacement vector points

a. to the right.

b. to the left.

c. has zero length.

d. cannot tell without more information.

4. Velocity vectors point

a. in the same direction as displacement vectors.

b. in the opposite direction as displacement vectors.

c. perpendicular to displacement vectors.

d. in the same direction as acceleration vectors.

e. velocity is not represented by a vector.

chocolatemouse942

An object moves clockwise with decreasing speed around an oval track. The velocity vectors at points G and H arc shown.

a. In the space at right, copy the velocity vectors and . From these vectors, determine the change in velocity vector .

b. If point H were chosen to lie closer to point G, describe how would change (direction and magnitude).

c. Describe how you would determine the acceleration (direction and magnitude) at point

G. In the space at right, indicate the direction of the acceleration of the object at point G.

d. Copy and (placed "tail-to-tail") in the space at right. How does the angle between the acceleration and velocity vectors compare to 900? (i.e., Is the angle greater than, less than, or equal to 90°?)

Generalize your results above and from tutorial to answer the following question:

For an object moving along a curved trajectory, how does the angle between the acceleration and velocity vectors compare to 90° if the object moves with (i) constant speed, (ii) increasing speed, and (iii) decreasing speed?

brownalpaca426

1. An object is dropped from a height.Once it is moving,which ofthe following statements are true,at least at one point?
a)its velocity is more than its accelerations
b)its velocity is less than its acceleration
c)its velocity is the same as its acceleration
d)its velocity is never equal to its acceleration

2. Which type of quantity is characterized by both magnitude anddirection?
a)scalar
b)vector
c)trigonometric
d)algebraic variable

3. A hiker walks 200m west and then walks 100m north. In whatdirection is her resulting displacement?
a)north
b)west
c)northwest
d)none of the answer is correct

4. Vector 1 is 7 units long and is at 70 degree. Vector 2 is 5units long and is at 225 degree. Vector 3 is a 3 units long and isat 150 degree. Which vector has equal magnitude components?
a)Vector 1
b)vector2
c)vector 3
d)none of the vectors has equal magnitude components??????

5. Which of the following is an example of the type of force thatacts at a distance?
a)gravitational
b)magnetic
c)electrical
d)all of the above

6. A crate weight W is being pushed across a horizontal surface bya force directed at an angle of 20 degrees below the horizontal.What is the magnitude of the normal force on the crate?
a)it is less then W
b)it equals W
c)it is more than W
d)none of the above since the coefficient of kinetic friction isnot given

7. The net force on an object is in the positive x-direction.Consider the following statements.
(i) The object can be moving in the negative x-direction.
(ii) The object can be speeding up.
(iii) The object can be slowing down.
(iv) The object can be moving in the positive y-direction.

Which of the statements are true?
a. (i) and (ii)
b. (ii) and (iii)
c. (iii) and (iv)
d. Choose this answer if all the statements are true.

8.The work done by static friction can be:
a. positive.
b. negative.
c. zero.
d. Any of the above.

9.The rate at which work is done is equivalent to which of thefollowing?
a. increase in potential energy
b. thermal energy
c. potential energy
d. power

10.The dimensional equivalent of the quantity impulse in terms ofthe fundamental quantities (mass, length,
time) is which of the following?
a. MLT-1
b. ML2T-2
c. MLT
d. MLT-2

11. The dimensional equivalence of the quantity "momentum" in termsof the fundamental quantities (mass,
length, time) is:
a. MLT-1.
b. ML2T-2.
c. MLT.
d. MLT-2.

12.In order for a satellite to be geosynchronous, its orbitmust:
a. go over the North and South Poles.
b. be over the equator.
c. be over a single longitude.
d. emit television signals.

13. The quantity "angular momentum" (in terms of the fundamentalquantities of mass, length, and time) is equivalent
to:
a. MLT-2.
b. ML2T-1.
c. ML2T-3.
d. ML3T.
d. MLT-2.

PHYS 2211K Lecture Notes - Lecture 2: Ruili

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