Intro to Conservation of Momentum Video Lessons

Concept

# Problem: A student standing on a stationary skateboard tosses a textbook with a mass of mb = 1.3 kg to a friend standing in front of him. The student and the skateboard have a combined mass of mc = 103 kg and the book leaves his hand at a velocity of vb  = 2.98 m/s at an angle of 41° with respect to the horizontal.(a) Write an expression for the magnitude of the velocity of the student, vs, after throwing the book.(b) Calculate the magnitude of the velocity of the student, vs, in meters per second. (c) What is the magnitude of the momentum, pe, which was transferred from the skateboard to the Earth during the time the book is being thrown (in kilogram-meters per second)?

###### FREE Expert Solution

Momentum, P,

$\overline{){\mathbf{P}}{\mathbf{=}}{\mathbf{m}}{\mathbf{v}}}$

The horizontal component of velocity,

mb = 1.3 kg, mc = 103 kg, ms = 103 - 1.3 = 101.7kg, v = 2.98 m/s, θ = 41°

a)

Conservation of momentum horizontally:

Pi = Pf

The momentum of the system initially is 0.

Therefore, the net momentum of the system after the book is thrown is 0.

Ps = Pb

After throwing the book, the student has the velocity, vs

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###### Problem Details

A student standing on a stationary skateboard tosses a textbook with a mass of mb = 1.3 kg to a friend standing in front of him. The student and the skateboard have a combined mass of mc = 103 kg and the book leaves his hand at a velocity of v = 2.98 m/s at an angle of 41° with respect to the horizontal.

(a) Write an expression for the magnitude of the velocity of the student, vs, after throwing the book.

(b) Calculate the magnitude of the velocity of the student, vs, in meters per second.

(c) What is the magnitude of the momentum, pe, which was transferred from the skateboard to the Earth during the time the book is being thrown (in kilogram-meters per second)?