Mechanics | Relativity Answers

3. A traffic light weighing 1 X10² N hangs from a vertical cable tied to two other cables that are fastened to a support as shown in the figure. The upper cable makes angles of 37° and 53° with the horizontal. Find the tension in the three cables.

4. The distance between two telephone poles is 50 m. When a 1 kg bird lands on the telephone wire midway between the poles, the wire sags 0.2 m. Draw a free-body

diagram of the bird. How much tension does the bird produce in the wire? Ignore the weight of the wire.

1. a.) Suppose a hockey puck slides down a frictionless ramp with an acceleration of 5 m/s². What angle does the ramp make with respect to the horizontal?

b) If the ramp has a length of 6 m, how long does it take the puck to reach the bottom?

c) Now suppose the mass of the puck is doubled, What will be it’s acceleration?

2. A space-walking astronaut of total mass 148 kg exerts a force of 265 N on a free-floating satellite of mass 635 kg, pushing it in the +x direction.

a. What is the reaction force exerted by the satellite on the astronaut?

b. Calculate the acceleration of the astronaut

c.The acceleration of the satellite

A 30 kg block is pushed up an inclined plane at an angle of 25° with a constant velocity of 4 m/s by a force of 280 N parallel to the plane.

What is the coefficient of kinetic friction between the block and the plane?

A uniform 10 kg ladder 2.5 m long is placed against a frictionless wall with its base on the ground 80 cm from the wall.

Find the magnitude of the force exerted on the wall and on the ground.

A 75 kg man is able to climb up 15 m in a 20 m ladder before it slips. What must be the coefficient of friction if the ladder is arranged so that its base makes at an angle of 50⁰ with the ground? Assume the ladder to be uniform and weighing 100 kg.

4. A uniform 15 kg ladder 3 m long rests against a frictionless wall at a point

2.4 m off the floor. Find the horizontal and vertical components of the force exerted by the ladder on the floor.

A satellite has a mass of 100 kg and is located at 2 X10⁶ m above the surface of the Earth.

a) What is the Potential energy associated with the satellite at this location?

b) What is the magnitude of the gravitational force on the satellite?

Solve the resultant and direction of the forces given by component and closed polygon method force 1= 100 grams, due east force 2= 120 grams 30° south of west force 3= 80 grams, 45° South of East?

A 100 kg object is taken to a height of 300 km above the Earth’s surface.

What is the object’s mass at this height?

What is the object’s weight at this point?

From the known mass and radius of the moon, compute the value of the acceleration due to gravity, gM at the surface of the moon.

(mass of the moon M = 7.35 X10²² kg) ( G = 6.67 X10⁻¹¹ Nm²/kg² )

(radius of the moon R = 1.7374 X10⁶ )