Chapter+2

__**Section 1**__ __**Physics to go**__ 1a) If you role a ball across a frictionless surface is will roll forever. 1b) Well if there is no force to act upon it, newton's first law of motin says that an object in motion will stay in motion with a constant speed, until a force acts upon it. If the surface is perfectly frictionless there is no force so the ball will continue to roll forever.

2) It will never reach a vertical height of 20 cm, it will reach close... like 18 cm, but never 20 cm.

3) It is not possible to "arrange conditions" to make an object move, unassisted, in a straight line at a constant speed forever because there are always going to be factors like friction or gravity that are going to act on the object and make it stop. Only in space

4) There is little friction between the ice and the hockey puck that is why the puck glides so easily across the ice. But when a force is put upon the puck, it stops it from continuing in its natural line of motion. A force was applied to the hockey puck-- it doesnt start moving until a force is applied and it doesnt stop until another force- or the same force- stops it. Newtons first law works in both ends of the scenario.

5) speed of ball + speed of wagon = ? (speed at which the person sees the ball go by) 2.5 m/s + 4.5 m/s = 7m/s

6) velocity + running start = velocity of javelin relative to the ground 10.3m/s + 4.2m/s =14.5 m/s

7a) train velocity + cart velocity = velocity of the cart relative to the ground 5.6 m/s + 2.4 m/s = 8m/s

7b) train velocity - cart velocity = velocity of the cart relative to tracks when it is moving toward the rear of the car 5.6m/s + -2.4 m/s = 3.2m/s

7c) The carts velocity relative to the ground is 5.6 m/s because it is moving the speed of the train.

8) velocity of the horse + velocity of the bow = speed of the arrow relative to the ground 18m/s + ? = 85 m/s velocity of the bow = 67 m/s

9) ball is released on a ramp of a vertical height of 15 cm how far up on the second ramp will the ball roll if the angle of the second ramp is a)45- 21.2 15/sin(45) b)20- 43.9 15/sin(20) c)15- 58 15/sin(15) d)5- 172 15/sin(5)

10.?

__**Section 2**__

1. Average Speed is a measure of the distance traveled in a given period of time. Instantaneous speed is how fast an object is going at a particular speed
 * Physics to go**

2. a) 1/ 15 = .07 km/ s b) 84/ 6 = 14 m/s c) 9.6/ 2 = 4.8 km/ h d) 400/ 4.5 = 88.9 km/ h

3. a) Yes, negative can be changing direction or speeding up or slowing down b) Yes, positive can be changing direction or speeding up or slowing down c) None d) Yes, positive can be changing direction or speeding up or slowing down e) None f) None

4. a) D b) B c) A d) C e) answers -A = Positive -B = None -C = Positive and Negative -D = Positive

5. (d2-d1) / (t2-t1) (s) || Length of 6-tick Segment (cm) || Average Speed (cm/s) || Calculations For 5
 * Total Elapsed Time
 * 0.1 || 0.7 ||  ||
 * 0.2 || 2.1 ||  ||
 * 0.3 || 3.5 ||  ||
 * 0.4 || 4.9 ||  ||
 * 0.5 || 6.3 ||  ||
 * 0.6 || 7.7 ||  ||
 * 0.7 || 9.1 ||  ||
 * 0.8 || 10.5 ||  ||
 * 0.9 || 11.9 ||  ||
 * 1.0 || 13.3 ||  ||
 * 1.1 || 14.7 ||  ||
 * 1.2 || 16.2 ||  ||

6. a. a = [(vf) - (vi)] / t a = [(0) - (45)] / 9 a = -5 km/h/s b. The acceleration has a negative value

7. a. constant b. positive acceleration c. positive --> negative d. negative --> positive

8. 100mi/2h = 50mi/h

9. No this does not mean the person's instantaneous speed was always 15 m/s because the automobile was not always going 15 m/s, that is just an average of the speeds the automobile was actually going.

10.

11. 1st second - 4m/s 2nd second - 8m/s 3rd second - 12m/s 4th second - 16m/s 5th second - 20m/s

12. Yes the sprinter can move faster than the cyclist because the average speed for the word-class sprinter is 10m/s which is faster than the average speed of the cyclist at 6 m/s

13. In relays, the runners are changing directions around the track. We know that acceleration is affected by speed and time and distance. In the 100m dash the runners are going in one direction: straight. In the relays they change all different directions which affects the acceleration. Also, the relay runners get a head start which can increase their acceleration.

14. a) bowling b) baseball c) bicycle riding b) bobsledding e) curling