MSU PHYS101 - Week 2 Assignment Solutions

MSU PHYS101 - Week 2 Assignment Solutions - Week 2...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Week 2 Assignment Questions - Phys 101 Online Energy and Conservation Laws (All references are from the text book: th ed. Belmont,CA: Thomson.) 1. A runner with a mass of 60kg accelerates from 0 to 9 m/s in 3 s. Fin the net force on the runner using the alternate form of Newton’s second law. (ref: pg 88) F = MA = M(∆V/∆T) where F is the force, M is mass, A is acceleration , ∆V is the change in velocity, and ∆T is the change in time. F = 60kg ( 9m/s / 3s) = 180 N 2. A 4000kg truck runs into the rear of a 1000kg car that was stationary. The truck and car are locked together after the collision and move with speed 10m/s. what was the speed of the truck before the collision? Compute how much kinetic energy was “lost” in the collision? (ref: pp. 89-93; 99-100; 111-114) a) First we must use momentum conservation to figure out the cars speed before collision. M 1 V 1 + M 2 V 2 = (M 1 + M 2 ) V 3 where M 1 is the mass of car, M 2 is the mass of truck, V 1 is the velocity of car prior to collision, V 2 is the velocity of truck prior to collision, and V 3 is the velocity of both locked vehicles. Since the car was stationary, V 1 = 0 Therefore: M 2 V 2 = (M 1 + M 2 ) V 3 4000kg V2 = (4000kg + 1000kg) 10m/s V 2 = 12.5m/s b) Now that we have the velocities prior to the collision, we can calculate the KE’s KE before = ½ M 2 V 2 = ½ 4000kg (12.5m/s) 2 = 312500J KE after = ½ (M 1 +M 2 ) V 3 = ½ (4000kg + 1000kg)(10m/s) 2 = 250000J KE change = KE after – Ke before = 250000J – 312500J = -62500J
Background image of page 1

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

View Full DocumentRight Arrow Icon
3. Two persons on ice skates stand face to face and then push each other away. Their masses are 50kg and
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/07/2010 for the course PHYSICS PHYS 101 taught by Professor Rademacher during the Spring '10 term at Mountain State.

Page1 / 4

MSU PHYS101 - Week 2 Assignment Solutions - Week 2...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online