Solutions to the old quiz

From J3 Physics

A copy of the quiz with the typos fixed:

Quiz copy--click to view or download

Answers:

1. a. "Does this quantity have a direction (and a magnitude)?"

b. Impulse must be a vector, since if it were a scalar the numbers would add traditionally, i.e. an impulse of 24 plus an impulse of 26 would give an impulse of 50.

2. Acceleration is always zero horizontally, so we can us the simpler equation

<m>s = \bar{v}t</m>

3.

First leg--> E: 30 m, N: 0 m

Second leg-->E: 16 m, N: 12 m

Third Leg--> E: 30 m, N: -40 m

Sum of components--> E: 76 m, N: -28 m

Solve for length with pythagorean theorem, solve for angle with inverse tangent.

4.

time = 42 m/12 m/s = 3.5 seconds (solved in the x-direction)

Vertical impact velocity = 35 m/s

Building height: h = v_avgt = 17.5*3.5 = 61.25 m

Overall impact velocity = <tex>sqrt{12^2 + 35^2}</tex> = 37 m/s

Impact angle = inverse tan of (35/12) (why?)

5.

v_0x = 24 m/s ; v_0y = 18 m/s

a. Peak: <tex>y: s_y = \bar{v}t = \frac{18+0}{2}*1.8 = 16.2 m</tex>

b. impact on wall occurs in 1.5 seconds, peak at 1.8 seconds so it's on the way up.

Height on wall is 15.75 meters (why?).

CCoe.