{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

# HW12 - schneiter(tcs639 – HW12 – Ross –(89152 1 This...

This preview shows pages 1–2. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: schneiter (tcs639) – HW12 – Ross – (89152) 1 This print-out should have 8 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points Betty weighs 440 N and she is sitting on a playground swing seat that hangs 0 . 48 m above the ground. Tom pulls the swing back and releases it when the seat is 0 . 79 m above the ground. The acceleration of gravity is 9 . 8 m / s 2 . How fast is Betty moving when the swing passes through its lowest position? Correct answer: 2 . 46495 m / s. Explanation: The swing moves from the highest position to the lowest. By conservation of energy, U o + K o = U f + K f mg h o + 0 = mg h + 1 2 mv 2 2 g h o = 2 g h + v 2 v = radicalbig 2 g h o- 2 g h = radicalbig 2 g ( h o- h ) = radicalBig 2 (9 . 8 m / s 2 ) (0 . 79 m- . 48 m) = 2 . 46495 m / s . 002 (part 2 of 2) 10.0 points If Betty moves through the lowest point at 1 . 4 m / s, what is the magnitude of the work done on the swing by friction? Correct answer: 92 . 4 J. Explanation: This time the swing does work against fric- tion, so U o + K o- W fr = U f + K f mg h o + 0- W = mg h + 1 2 mv 2 1 W = mg h o- mg h- 1 2 mv 2 1 W = F w h o- F w h- 1 2 F w g v 2 1 = (440 N) (0 . 79 m)- (440 N) (0 . 48 m)- 1 2 parenleftbigg 440 N 9 . 8 m / s 2 parenrightbigg (1 . 4 m / s) 2 = 92 . 4 J . 003 10.0 points A block of mass 0 . 16 kg is placed on a verti- cal spring of constant 7467 N / m and pushed downward, compressing the spring 0 . 08 m....
View Full Document

{[ snackBarMessage ]}

### Page1 / 4

HW12 - schneiter(tcs639 – HW12 – Ross –(89152 1 This...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online