# Applying Newton's second law

1) A cannon shoots a ball at an angle above the horizontal ground. (a) Neglecting air resistance, use

Newton's Second Law to find the ball's position as a function of time. (Use axes with x measured

horizontally and y vertically.) (b) Let r(t) denote the ball's distance from the cannon. What is the

largest possible value of if r(t) is to increase throughout the ball's flight? [Hint: Using (a)'s solution

you can write down r^2 as x^2 + y^2, and then find the condition that r^2 is always increasing.]

2) An astronaut in gravity-free space is twirling a mass m on the end of a string of length R in a circle, with

constant velocity w. Write down Newton's second law in polar coordinates and find the tension in the

string.

3) A slab of mass M1 = 40.0 kg rests on a frictionless floor, and a block of mass M2 = 10.0 kg rest on top

of this slab. Between the block and slab, the coefficient of static fraction is 0.60, and 0.40 is the

coefficient of kinetic friction. A horizontal force of 100 N is applied to the block (on top of slab). What

are the resulting accelerations of the block and slab? You must draw pictures and Free Body Diagrams

to get full credit.

4) A student wants to determine the coefficients of static friction and kinetic friction between a box and a

plank. She places a box on the plank and gradually raises one end of the plank. When the angle of

inclination with the horizontal reaches 30°, the box starts to slip, and it then slides 2.5 m down the plank

in 4.0 s at constant acceleration. What are (a) the coefficient of static fraction and (b) the coefficient of

kinetic fraction between the box and the plank? You must draw pictures and Free Body Diagrams to get

full credit.

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#### Solution Summary

This solution provides step by step calculations for various questions that apply the use of Newton's second law.

Applying Newton's Law for a wagon (M) attached by string with hanging mass (m) through frictionless pulley.

See the attachment for a diagram and the data in a chart before answering the following problem.

The mass of the wagon (M) and the hanging mass (m) are in kilograms. The total mass of the system is Mt, the sum of M and m. The acceleration of gravity (g) is 9.8 m/s2 . The acceleration of the system (a) varies, depending upon the experimental values of M, m, and µ. In the situation shown above (μ = 0), the only force acting on the system is the weight of the hanging mass, Wm.

Fill in the following table, using the value of a obtained from the simulation. Record and calculate data to the nearest three decimal places. The masses in the table are in kg, but the input data are in grams, so make the necessary conversions. The first row has been completed for you.

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