I have some questions as homework, and for some, it would be nice to know whether or not my answers are wrong. I need guidance on one of the questions, and I have no idea where to start on other. Our physics teacher is making us start from the back of the book (nuclear physics) and move forwards. That means, I really have no concrete knowledge of anythign that comes before chapter 7 (momentum), and that's why I think I'm having a lot of problems with it. All help is appreciated. And I'm too slow with the latex, so I hope this work is okay..(adsbygoogle = window.adsbygoogle || []).push({});

A car of mass 1100 kg moves at 24 m/s. What braking force is needed to bring the car to a halt in 20 s?

Breaking force = mv/t = (1100 kg)(24 m/s)/20 s =1.32x10^3 N

What average force is exerted on a 25-g egg by a bed sheet if the egg hits the sheet at 4 m/s and takes 0.2 s to stop?

p=mv, = (0.025 kg)(4 m/s), = 0.1 kg (m/s)

pfinal = 0

deltap = pfinal - pinitial = 0 - 0.1 kg (m/s)

f = -.01 kg (m/s) / .02

=-(1/2)kN

a 100-kg quarterback is traveling 5 m/s and is stopped by a tackler in 1 s. Calculate (a) the initial momentum of the quarterback, (b) the impulse imparted by the tackler, and (c) the average force exerted by the tackler.

(a) momentum = mv = (100kg)(5 m/s) =500 kg (m/s)

(b) p = 500 kg (m/s), deltap = 0 - 500 kg (m/s) =-500 kg (m/s)

(c)average force - deltap/t = -500 kg (m/s)/1s =-500 kN

A 40-kg football player going through the air at 4 m/s tackles a 60-kg player who is heading toward her at 3 m/s, in the air. What is the speed and direction of the entangled players?

I'm not really sure how to solve this problem... I know they are vector forces, but are they drawn like this: ----> <------ or are they at a different angle? And to find the speed, you would use c^2 = a^2 + b^2, but this isn't a right triangle, or I don't think, so what do I use. And I know to find the angle you usually use inverse tangent, but, can you in this case?

A jet engine gets its thrust by taking in air, heating and compressing it, adn then ejecting it at a high speed. If a particular engine takes in 20 kg of air per second at 100 m/s, and ejects it at 500 m/s, calculate the thrust of the engine.

What is the equation I use to find the thrust of the engine?

A 40-kg projectile leaves a 2000-kg launcher with a speed of 400 m/s. What is the recoil speed of the launcher?

I'm not sure, but here is my work:

momentum = mv = (40kg)(400 m/s) = 16,000 kg (m/s)

mlauncher*vlauncher = -mprojectile*vprojectile = -(16,000 kg (m/s))

vlauncher = -16,000 kg (m/s) / 2000 kg =-8 m/s

A car of mass 1400 kg travels at 20 m/s and collides with a stationary truck of mass 2800 kg, with its parking brake off. The two vehicles interlock as a result of the collision and slide along the icy road. What is the velocity of the car-truck system?

(1400 kg)(20 m/s) = (1400 kg + 2800 kg)*v

28,000 kg (m/s) = 4200kg*v

v = 28,000 kg (m/s) / 4200 kg =6.7 m/s

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# Homework Help: Momentum and Breaking force of car

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