Mechanics | Relativity Answers

A ball is thrown at 22 m/s at 45 degrees to the horizontal. A 5 foot tall fence is located 100 meters away. Does
the ball make it over the fence?

A rock thrown horizontally from a bridge hits the water below 30 meters away in the horizontal direction. If
the rock was in the air for 2 seconds, how tall is the bridge?

Calculate the force of gravity between Earth and the moon

A boat begins on the best side of a river and heads straight east across the river with a speed of 1.9 Ft/s (relative to the water). the river water flows NORTH at the speed of 2.^ Ft/s (relative to the shore). The resultant velocity of the boat ( relative to the shore) is approximately ___ Ft/s at __ degrees (-CCW from east)

A puck of mass 30.0kg slides across rough ice, experiencing a frictional force of 0.20 N. If it was moving at 10.0 km/h when it hit the ice patch, how long did it take to stop?

A rock thrown horizontally at 25 m/s from a cliff that is 45 m high. How far from tag base of the cliff does the rock land?

4. A steel ball of mass m is fastened to a light cord of length L and released when the cord is horizontal. At the
bottom of its path, the ball strikes a hard plastic block of mass M = 3m, initially at rest on a frictionless
surface. The collision is elastic.
(a) Find the tension in the cord when the ball’s height above its lowest position is L/3. Write your answer
in terms of m and g.
(b) Find the speed of the block immediately after the collision.
(c) To what height h will the ball rebound after the collision?

3. A solid disk of radius 0.50 m and a mass of 0.10 kg is moving with a linear or translational velocity of 5.00 m/s. Determine the disk’s:
a. Translational kinetic energy.
b. Rotational kinetic energy if rotating while translating.

1. A turntable is initially rotating a 1.50 rad/s and accelerates at 2.50 rad/s for 5.0s.
a) Calculate the final angular velocity in rad/s
b) Compute the angular displacement during the 5.0 s in radians and revolutions

A car of mass 1000 kg is cruising at 90 km/hr. At this velocity the drag and friction forces that the engine needs to work against is equivalent to 250 N.
The propulsive power delivered at the wheels is equal to 6250 Watts. The mechanical efficiency of the wheel hubs and transmission driveline is given as 97%. The mechanical efficiency of the gearbox is given as 92%.


Q: Calculate the power that the engine needs producing in order to deliver a propulsive power at the wheels of 6250 Watts?
Give your answer in Watts