Physics Work,Power & Energy Level: High School
Your rich aunt sent you a few hundred dollars , with which you just bought a new Ferrari at Wynn Las Vegas . You are out tooling around the back roads of Nevada when you spot an escaped alien from Area 51 sauntering across the road ahead . To avoid the intergalactic incident that would occur had you run over this creature , you slam on the brakes , noting that you were going 150 miles per hour , Assume that the antilock brake system kicks in to keep the tires from skidding and that your supergrip tires have a static coefficient of friction of 0.95. Also , assume the mass of your new car is 1.30 x 10^3 kg , and the mass of the steel brake rotors is 4.00 kg each . (Remember , like most cars , Ferraris have four wheels , too )a) How fast were you going initially ,in meters per second ?
b) How far does it take for the car to stop ?
c) How much work was done by friction to slow down and stop your car ?
d) Was this work positive or negative ?
e) What was the initial kinetic energy of thecar and how does this relate to the frictional work ?
f) How much hotter did the brake rotors get as you stopped ,assuming no heat leaked from them ?
Physics Work,Power & Energy Level: High School
a) How much work must the Stratosphere elevator do to raise you and you friend (masses of 75.0 kg and 60.0 kg ) from the ground to the restaurant at the top ?
b) What is the minimum power rating for the elevator motor if the elevator must be able to carry 10 overweight conventioneers for 10 burly ex-XFL players ) of mass 150.0 kg each , along with the elevator mass of 1.50 x 10^3 kg , from the ground to the top in 60.0 seconds ?
Physics Work,Power & Energy Level: High School
Select which one of the following statement are true .a) The power required to lift a mass does not depend on the speed at which the mass is raised .
b) The work required to lift a mass one meter does not depend on the speed at which mass is raised .
c) Net work can be done on an object without changing it’s kinetic energy .
d) The work done by a constant force acting on an object depends on the orientation of the force relative to the motion of the object .
e) Conservation of energy means that the mechanical energy can never change .
Physics Work,Power & Energy Level: High School
Vertical Circle
A stone of mass 15.50 kg is attached to a strong string and whiled in vertical circle of radius 60 cm. At the exact top of the path , the tension in the string is 3.7 times the stone’s weight . What is the speed of the stone at this position (top of its path ) ?a) 3.95 m/s
b) 5.26 m/s
c) 6.99 m/s
d) 9.30 m/s
e) 1.24 x 10^-1 m/s
Physics Work,Power & Energy Level: High School
As your friend the skateboarder is in the middle of moving up a curved ramp , which of the following statements are true ? (All statements apply to the magnitudes of velocity , acceleration and force )a) Your friend’s acceleration is decreasing .
b) The normal force on your friend is decreasing .
c) The net force on you friend is zero .
d) You friend’s velocity is decreasing .
e) The gravitational force on your friend is constant .
Physics Work,Power & Energy Level: High School
Conservation of Energy
A lead ball (specific heat = 1.3 x 10^2 J/kg degree C) , at an initial temperature of 25 degree C , is released from a height of 92.0 m . It does not bounce when it hits a hard surface . If all the energy of the fall goes into heating the lead , find the temperature (in degrees C ) of the ball after its hits .a) 2.40 x 10^1 C
b) 3.19 x 10^1 C
c) 2.45 x 10^1 C
d) 5.65 x 10^1 C
e) 7.51 x 10^1 C
Physics Work,Power & Energy Level: High School
Two equal mass balls (one red and other blue ) are dropped from the same height, and rebound of the floor . The red ball rebounds to a higher position than the blue ball . Neglect air resistance . Which one of the following statement is / are true about this statement .a) The red ball is subjected to the greater impulse during the collision with the floor .
b) Once they come to a stop in the air after bouncing off the floor , both balls have the same of potential energy .
c) Except for the instant they collide with the floor , both balls are in free fall .
d) During the collision with the floor , both ball transfer the amount of momentum to the floor .
e) Mechanical energy is conserved for both balls.
Physics Work,Power & Energy Level: High School
Conservation of Energy
A bullet (m = 0.025 kg) is fired with a speed of 95.0 m/s and hits a block (M = 2.80 kg) supported by a string . Find the height to which the block rises .a) 3.60 x 10^-2 m
b) 4.79 x 10^-2 m
c) 6.37 x 10^-2 m
d) 8.48 x 10^-2 m
e) 1.13 x 10^-1 m
Physics Work,Power & Energy Level: High School
Conservation of Energy
A 26.0 kg child slides down a long slide in a playground . She starts from rest at a height h1 of 18.0 m . When she is partway down the slide , at a height h2 of 5.00 m , she is moving at a speed of 7.90 m/s . Calculate the mechanical energy lost due to friction (as heat etc. )a) 1.02 x 10^3 J
b) 1.28 x 10^3 J
c) 1.60 x 10^3 J
d) 2.00 x 10^3 J
e) 2.50 x 10^3 J
Physics Work,Power & Energy Level: High School
Bungee Jumping
Calculate a bungee cord of unstretched length L0 = 49 m . When the cord is stretched to L>Lo it behaves like s spring and obeys Hooke’s law with the spring constant k = 36 N/m . However , unlike a spring ,the cord folds instead of becoming compressed when the distance between its ends is less than the unstretched length: For L
Physics Work,Power & Energy Level: High School
A block starts at rest and slides down a frictionless track except for a small rough area on a horizontal section on the track (as shown in the figure below ) . It leaves the track horizontally , flies through the air , and subsequently strikes the ground . The acceleration of gravity is 9.81 m/s^2 . At what height h above the ground is the block released ?a) What is the speed of the block when it leaves the track ?
b) What is the total speed of the block when it hits the ground ?
Physics Work,Power & Energy Level: High School
Elastic Potential Energy
The force required to stretch a Hooke’s-law spring varies from O N to 21.1 N as we stretch the spring by moving one end 9.91 cm from its unstressed position . Find the force constant of the spring .a) Find the work done in stretching the spring .
Physics Work,Power & Energy Level: High School
Work Energy Theorem
A 0.39 kg particle has a speed of 3.5 m/s at point A and kinetic energy of 6.7 J at point B .a) What is its kinetic energy at A ?
b) What is the particle’s speed at B ? c What is the work done on the particle as it moves from point A to B ?
Physics Work,Power & Energy Level: High School
Work Energy Theorem
A mechanical pushed a 2416 kg car from rest to a speed of v, doing 3149 J of worked in the process . During this time , the car moves 22 m . Neglecting friction between the car and the road . Find v .a) Find the horizontal force exerted on the car .
Physics Work,Power & Energy Level: High School
Kinetic Energy
A 15-kg child stroller is moving towards you with a speed of 2.5 m/s . How much work is required to stop the stroller ?a) 19 J
b) 38 J
c) 47 J
d) 94 J
e) 460 J
