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ASSINGMENT 4 - Coggle Diagram
ASSINGMENT 4
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GPE:
EX1:
a) An object has a mass of 6kg. Calculate it's potential energy:
i)6m above the ground.
ii)12m above the ground
b)At what height above the ground will its potential energy be 420J?
EX4:
A stone has a mass of 30kg. Dropped form a cliff top, the stone strikes the sea below with a velocity of 15m/s.
i)What is the kinetic energy of the stone as it is about to hit the sea?
ii)What was it's potential energy before it was dropped?
iii)From what height was the stone dropped?
EX2:
Determine the work done by the force F,exerted on the block. Let F = 5N & the displacement s = 2m. Assume that the displacement of the block is to the right.
1- Force is in the upward direction.
2- The force is directed to the left.
3- The force is directed to the right.
4- F is directed to the left at about 30 degree from the horizontal.
5- F is directed to the right at about 30 degree from the horizontal.
EX2:
A stone has 160J of potential energy. What will be it's potential energy if it's height above the ground is halved?
Assume g= 10 m/s^2
Work
EX1:
Determine the signage of work in each case.
i- The force & displacement are in the same direction.
ii-The force is directed upward. There is no displacement.
iii-The force & displacement are in the opposite direction.
EX3:
A block of mass m = 2.50 kg is pushed a distance d = 2.20 m along a friction-less, horizontal table by a constant applied force of magnitude F = 16.0 N directed at an angle θ = 25.0° below the horizontal as shown in the figure. Determine the work done on the block by
(a) the applied force
(b) the normal force exerted by the table
(c) the gravitational force
(d) the net force on the block
KE:
EX1:
A 2kg box is pushed through a slippery floor. Its initial speed is 1.5 m/s. If the coefficient of kinetic friction is 0.7,how far does it travel??
Power
EX1
A crane lifts a 8000 N beam 75 m to to the top of a building in 30 s. How much power does the crane use?
EX2:
Using energy considerations and assuming negligible air resistance, show that a rock thrown from a bridge 20.0 m above water with an initial speed of 15.0 m/s strikes the water with a speed of 24.8 m/s independent of the direction thrown.
EX3:
If a spring is stretched 2.0 cm by a suspended object having a mass of 0.55 kg.
(i) What is the force constant of the spring.
(ii) How much work done by the spring as it stretched through this distance?
EX2:
The driver of an 1800 kg car (including passengers) travelling at 23.0 m/s slams on the brakes,locking the wheels on the dry pavement. The coefficient of kinetic friction between rubber and dry concrete is typically 0.700.
(i) Use the work-energy principle to determine how far the car will travel before stopping.
(ii) How far would the car travel if it were going twice as fast?
(iii) What happened to the car's original kinetic energy?
EX6:
The ball in the diagram has a mass of 3kg. 100J of work were done in moving the ball up the smooth slope from D to A.
i)What is the potential energy of the ball at A?
ii)If the ball falls, what is it's potential energy
at B, the mid point of it's fall?
iii)What is it's kinetic energy at B?
iv)If the ball were to roll back down the slope rather then fall, what would be it's kinetic energy as it reached D?
The Law of Conservation of Energy
EX1:
At the very top of a roller coaster, a girl has a potential of 100 J. What would be her kinetic energy at the very bottom of the hill,assuming the re is no energy lost to air (resistance)?
EX5:
a) How much electrical energy would be used by an elevator lifting a 75 kg person through a height of 50 m if the elevator system has an overall efficiency of 25%? Assume the mass of the empty elevator car is properly balanced by a counterweight.
b)What is the cost of the elevator journey assuming the cost of electricity is 0.10$/ kW.hour
EX4:
A tired squirrel (mass of 1 kg) does push-ups by applying a force to elevate its center-of-mass by 5 cm. Estimate the number of push-ups that a tired squirrel must do in order to do a approximately 5.0 Joules of work.
EX3:
An object of mass 8kg is travelling with a velocity of 6m/s.
i)What is it's kinetic energy?
ii)What will be it's kinetic energy if it's velocity is doubled?