Mechanics | Relativity Answers

A hollow metal sphere of outside diameter of 10 cm weighing 5gm/cm3 in air floats half submerged in fresh water. Determine the radius of the cavity

Mary and Sally are in a foot race (see figure (Figure 1)). When Mary is 22 m

m from the finish line, she has a speed of 4.0 m/s

m/s and is 5.0 m

m behind Sally, who has a speed of 5.0 m/s

m/s. Sally thinks she has an easy win and so, during the remaining portion of the race, decelerates at a constant rate of 0.43 m/s

2

m/s2 to the finish line.

Part A

What constant acceleration does Mary now need during the remaining portion of the race, if she wishes to cross the finish line side-by-side with Sally?

a 71kg diver drops from a board 10m above the water surface. use conservation of mechanical energy to find his speed 5m above the water surface.

A 25 kg object moving with a velocity of 3.0 m/s to the right collides with a 15 kg object moving to the left at 6.0 m/s. Find the velocity of the 25 kg object after the collision, if the 15 kg object continues to move to the left but only at 0.30 m/s

A 0.1 kg ball moving at a constant velocity of 2 m/s strikes a 0.4 kg ball that is at rest. After the collision, the first ball rebounds straight back at 1.2 m/s. Calculate the final velocity of the second ball

When the air resistance is ignored, the horizontal range R of a projectile is given by R(8)= 9 sin 20 where is the constant initial velocity, g is the acceleration due to gravity, and is the angle of elevation or departure. Find the maximum range of projectile.

1.   A volleyball player serves a ball with his height of 1.5-meter height and strikes the floor at point three meter horizontally.

a.   Time of flight of the ball

b.   Its horizontal velocity

A lift is reported to operate at 75% efficiency. If the lift can raise a load through a height of 30m using a 230V, 15A supply, calculate how long it will take to raise a load of 1000Kg.

A motor and gearbox system are used to raise a load from the ground to the roof. The load weighs 100Kg and the motor fed from supply of 110v and draws 15A. If the roof is 25m above the ground, calculate: a) The PE of the load when it has been raised, b) The amount of electrical energy used in that time

A student eats a dinner containing 2000Calories of energy. He wishes to do an equivalent amount of work in the gymnasium by lifting a 10Kg object. How many times must he raise the object to expand this much work? Assume that he lies to his back and raises it a distance of 0.5m each, and the effort done to let the weight down is 50% of the effort done to raise it.