Download PROBLEMS conservation of energy/energy/work 1.A)How much

PROBLEMS conservation of energy/energy/work
1.A)How much work is needed to hoist a 98N sack of grain to a storage room 50m above the ground
floor of a grain elevator?
B)What is the potential energy of the scak of grain at this height ?
C)The rope being used to lift the sack of grain breaks just as the sack reached the storage room. What
kinetic energy the scak have before to strikes the floor ?
2.An Archer puts a 0.3kg arrow to the bowstring. An average force of 201N is exerted to draw the
string back 1.3m
A)Assuming no frictional force, with what speed does the arrow leave the bow ?
B)If the arrow is shot straight up, how high does it rise ?
3)A 1200kg car starts from rest and accelerates to 72km/h in 20s. The average force needed to
overcome the force of friction during this period is 450N. (meaning friction force=450N)
A) What distance does the car move duringt his period of acceleration (kinematics)
B)What force does the engine produce during its period of acceleration ?
(work-energy theorem change in kinetic energy = sum of individual force = F X – 450X)
C)How much work does the engine do to accelerate the car ?
4)A force of 410N is applied in a direction straight up to a stone that weighs 32N. If the force is applied
through a distance of 2m, to what height from the point of release, will the stone rise ?
5)A 20kg mass is on the edge of a 100m high cliff. What potential energy does it possess ?
B)The mass falls from the cliff. What is its kinetic energy before it strikes the ground ?
6)A steel ball has a mass of 4kg and rolls along a smooth level surface at 62m/s.
A)Find its kinetic energy
B) At first the ball was at rest on the surface. A force acted on it through a distance of 22m to give it the
speed of 62nm/s. What was the magnitude of the force?
7)A 420N boy sits in a swing seat that hands 0.4m from the ground. A firend pulls the swing back so
that the seat is 1, from the grounf and releases the swing.
A) How fast will the boy on the swing be moving when the swing passes through its lowest position ?
B)If the boy moves through the lowest point at 2m/s , how much work was done on the swing by the
friction ?
8) A 10g ball is projected straight down from a height of 1m. It strikes the floor at a speed of 5.5m/s.
What was the initial velocity of the ball ?