Physics problems: dynamics

Part 3



Problem 21.

Starting from rest, a skier slides 200 m down a 35 degrees slope. How much longer does the run take if the coefficient of kinetic friction is 0.3 instead of 0?



Problem 22.

A soccer ball of diameter 35 cm rolls without slipping at a linear speed of 2 m/s. Though how many revolutions has the soccer ball turned as it moves a linear distance of 20 m?



Problem 23.

A bicycle is moving at 10 m/s.  What is the angular speed of its tires if their radius is 30 cm?



Problem 24.

The gravitational force that the sun exerts on the moon is perpendicular to the force that the earth exerts on the moon.

The masses are: Mass of Sun , Mass of Earth: ,, Mass of Moon: . The distance between the sun and moon is , and between the moon and the earth is .

Determine the magnitude of the net gravitational force on the moon.



Problem 25.

A tension of 6000 Newtons is experienced by the elevator cable of an elevator moving upwards with an acceleration of . What is the mass of the elevator?





Problem 26.

What conditions are necessary for an object to move with constant velocity?

What conditions are necessary for an object to move with constant acceleration?



Problem 27.

Consider a wet roadway banked, where there is a coefficient of static friction of 0.40 and a coefficient of kinematic friction of 0.2 between the tires and the roadway. The radius of the curve is R=80m

(a) if the banking angle is 30,what is the maximum speed the automobile can have before sliding up the banking?

(b) What is the minimum speed the automobile can have before sliding down the banking?



Problem 28.

Is it easier to move a heavy box that is sitting on the ground by (a) pulling the box from a rope that makes an angle with the surface or (b) by pushing the box with a force that makes the same angle (but pointing downwards) with the surface?



Problem 29.

The space shuttle is orbiting the Earth at a distance of about 300 km from its surface. At that distance, the gravitational acceleration is almost the same as that on the surface. How long does it take for the shuttle to complete one orbit around the Earth? Assume that the orbit is circular.

Disregard air resistance.



Problem 30.

A spaceship is on a straight-line path between Earth and moon. At what distance from the Earth is net gravitational force on the spaceship zero?





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