Physics questions?

Announcements(1)100 new clickers alleged to arrive by Friday 

9/12.(2)“Want an A”  ­ R.Cormack 7­9 pm Cramer 124 

(Thursday)(3)Reminders about course home­page and MP 

help.

Outline(1)Acceleration on curved paths(2)Projectile Motion

                     in 3­Dr=3t2 i−4t4 j11t7 k

What is the instantaneous acceleration at t=2? 

vand a

a=6 i−192 j m /s2

Acceleration parallel to velocity

a=d vdt

Acceleration not parallel to velocity

a=d vdt

6.1   2­D AccelerationAn object undergoes acceleration of 

over a 10­s interval.  

At the end of that time, its velocity is

What was its velocity at the beginning of the interval?

IDENTIFY EQUATION NEEDED:

a)

b)

c)

d) There is more than one correct answer

a=2.3i3.6 j m /s2

33 i15 j m /s2

aAV= v

dt

v= v0a t

r=r0v0 t+ 12 a t2

6.1   2­D AccelerationAn object undergoes acceleration of 

over a 10­s interval.  

At the end of that time, its velocity is

(a) What was its velocity at the beginning of the interval?

(b) How much did its speed change?

(c) How much did its direction change?

(d) The speed change is not given by the magnitude of the acceleration multiplied by the time.  Why not?

a=2.3i3.6 j m /s2

33 i15 j m /s2

What is the direction of the object’s average acceleration vector for the time interval from t = 0 to t = t1?

A. up and to the left

B. up and to the right

C. down and to the left

D. down and to the right

E. none of the above

1

Q

What is the direction of the object’s average acceleration vector for the time interval from t = 0 to t = t1?

A. up and to the left

B. up and to the right

C. down and to the left

D. down and to the right

E. none of the above

1

A

The motion diagram shows an object moving along a curved path at constant speed. At which of the points A, C, and E does the object have zero acceleration?

A. point A only

B. point C only

C. point E only

D. points A and C only

E. points A, C, and E

Q

The motion diagram shows an object moving along a curved path at constant speed. At which of the points A, C, and E does the object have zero acceleration?

A. point A only

B. point C only

C. point E only

D. points A and C only

E. points A, C, and E

A

Outline(1)Acceleration on curved paths(2)Projectile Motion

An object moves at a constant speed in a clockwise direction around a circular track. The geometrical center of the track is at point O. When the object is at point P, which arrow shows the direction of the object’s acceleration vector?

A. arrow #1 (directly away from O)

B. arrow #2 (perpendicular to track)

C. arrow #3 (in direction of motion)

D. arrow #4 (directly toward point O)

# 1

# 5

# 4

# 3# 2

P

O

o v a l t r a c k

Q3.4a

An object moves at a constant speed in a clockwise direction around a circular track. The geometrical center of the track is at point O. When the object is at point P, which arrow shows the direction of the object’s acceleration vector?

A. arrow #1 (directly away from O)

B. arrow #2 (perpendicular to track)

C. arrow #3 (in direction of motion)

D. arrow #4 (directly toward point O)

# 1

# 5

# 4

# 3# 2

P

O

o v a l t r a c k

A3.4a

A zoo keeper fires a tranquilizer dart directly at a monkey. The monkey lets go at the same instant that the dart leaves the gun barrel. The dart reaches a maximum height P before striking the monkey. Ignore air resistance. 

Does the dart hit the monkey?

Monkey and hunter

Projectile Range

A projectile is launched at velocity v and angle theta.  What is its range?

  Relative velocityAgent 007 drives a lunar buggy at constant velocity

along the lunar surface.

He fires a missile traveling

at 600 m/s with a heading

30 degrees South of West.

One minute later a base 

20 km due west of the 

launch point is destroyed.

What is Bond's heading and speed?