1-d Motion: Kinematics

You are driving home from school steadily at 95 km/h for 130 km.

It then begins to snow and you slow to 65 km/h. You arrive home

after driving 3 hours and 20 minutes.

A. How far is your hometown from school?

B. What was your average speed?

At highway speeds, a particular automobile

is capable of an acceleration of about 1.6 m/s^2

At this rate, how long does it take to accelerate

from 80 m/s to 110 m/s?

**These are important, let get to know them.**

260 km

77 km/h

**19 s**

Questions

Goals for today

Practice

bit better understanding of velocity and acceleration

Equations of motion defined

Reading questions and gleaning data

Equation of motion usage

Lets practice reading and gathering info. (also equation recognition)

Another one

Which of the following is not possible

(while we're waiting think of examples for each)

A. Constant velocity and zero acceleration

B. Zero velocity and zero acceleration

C. Zero velocity and constant acceleration

D. Constant velocity and constant acceleration

E. Both C and D are not possible

F. Both A and C are not possible

G. Both A and D are not possible

H. Only B is possible

**A car traveling 95 km/hr is 210 m behind a truck traveling 75 km/hr. How long will it take the car to reach the truck?**

**Two locomotives approach each other on parallel tracks. Each has a speed of 155 km/hr with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other.**

**Your turn,**

**key in A if your done, B if you need more time, C if your lost**

**note no accelerations...**

Again with acceleration

A light plane must reach a speed of 35.0 m/s for take off. How long a runway is needed if the (constant) acceleration is 3.00 m/s^2 ?

In coming to a stop, a car leaves skid marks 65 m long. Assuming an acceleration of 4.00 m/s^2 slowed this car down, estimate the speed of the car just before braking?

key in A -Done B- Time C - Lost

A world-class sprinter can reach a top speed of about 11.5 m/s in the first 18.0 m of a race. what is the average acceleration of this sprinter and how long does it take her to reach that speed?

**38 s**

**99 s**

204 m

22.8 m/s

3.67 m/s^2

3.13 s

14.7 m

9.39 m/s

If her competition can only have an average acceleration of 3.00 m/s^2 during the same time interval

how far would she have traveled, and what is her final velocity?

We are getting questions about 3 main things

vectors!!!!

instantaneous velocity

main kinematic equations

"Can you go over real quickly the average velocity and acceleration"

"Out of the 4 constant acceleration equations, how do you know which one to use for each problem? "

"Did I do something wrong? This is what we covered in class today... "