1. What do we want to do today?! Tuesday: 29-1-1440
A bit of housekeeping
Conclude chapter-7
(possibly) introduce chapter-8
Prof. Zain Yamani
Office: / 3102; Phone: ; Mobile:
HP:

2. A bit of housekeeping
Attendance
If you come late, please make me aware during the (end of) the same lecture.

3. A bit of housekeeping
Mathematica is presumably available in:
Building 4/104
Building 7/ 137
Building 66/230
Library

4. A bit of housekeeping
Raise your hand if you are committed to attending a Help Session tomorrow (Wednesday) at 5.45 – 7.00 p.m.

5. Challenge: add friction!! 
A racing car speeds on a circular (radius: R) track that is banked at angle (q) with the horizontal. The car mass is (m) and the coefficient of static friction between car and track is m.
Draw a schematic of the problem.
Calculate the maximum speed that the car can run without skidding off.
In what ways can this “maximum” speed be improved?

7. Chapter-7: Energy
Kinetic Energy
Work
Work done by Weight (gravity)
Work done by Spring
Power

8. What did we learn about last lecture?

9. A rope exerts a force F on on a 20
A rope exerts a force F on on a 20.0 kg crate in lifting it vertically upward above the floor. The crate starts from rest and accelerates upward at 5.00 m/s2.
How much work was done by the force F in raising the crate 4.00 m above the floor?
A) kJ
B) kJ
C) kJ
D) kJ
E) kJ
101-2

10. What if the work is done by a spring?
The relaxed: non-stretched/ non-extended, non- compressed state.
The spring force is a (linear) “restoring” force.
Spring (or Force) constant: k
F = - k d
What does big “k” mean?
SI units for “k”?

11. What is the relation between their speeds at the instant of launch?
Two balls are launched from the same spring-loaded cannon with the spring compressed the same distance each time. Ball A has a 40 kg mass and ball B has a 60 kg mass.
What is the relation between their speeds at the instant of launch?
141-2

12. What is the relation between their speeds at the instant of launch?
Two balls are launched from the same spring-loaded cannon with the spring compressed the same distance each time. Ball A has a 40 kg mass and ball B has a 60 kg mass.
What is the relation between their speeds at the instant of launch?
141-2

13. Work done by a general variable force
(omitted)

14. Average and Instantaneous Power
P, units of P
Pavg
Pinstanaeous
The horsepower = 746 watt

15. The tension force is parallel to the incline.
A constant tension force is used to pull a 50.0 kg box up a frictionless plane inclined at 30.0° relative to the horizontal.
The tension force is parallel to the incline.
The box is moved a distance of 30.0 m along the incline with a constant speed of 1.00 m/s.
At what rate is work done by the tension force?
A) 245 W
B) 49.3 W
C) 98.0 W
D) 292 W
E) 495 W
101-2

16. A 0.50 kg object, moving along the x-axis, experiences the force shown in the Figure.
The object’s velocity at x = 0.0 m is v = 2.0 m/s, and at x = 4.0 m is v = 8.0 m/s. What is Fmax?
A) 5.0 N
B) 7.2 N
C) 9.7 N
D) 3.2 N
E) 1.8 N
101-2