Exam 6: Conservation of Energy

If the escape speed of a star is equal to the speed of light,its radius is the so-called Schwarzschild radius.What is the Schwarzschild radius of the sun,whose mass is 2.0 $\times$ 10³⁰ kg?

A 200 N box is pushed up an incline that is 5.00 m long and rises 1 m.If the incline is frictionless,then the work done by the pushing force is

A 120 N force is applied at an angle of 30.0 degrees above the horizontal to a 4.00 kg box.The box moves a horizontal distance of 8.00 meters.The change in the kinetic energy of the box is

A 2,000 kg car traveling at 30.0 mi/h skids to a stop in 60.0 meters.The force of friction during the skid is (1.0 mi/h = 0.447 m/s)

A 3.00 kg pendulum bob on a string 2.00 m long is released with a velocity of 2.00 m/s when the support string makes an angle of 45.0 degrees with the vertical.What is the tension in the string at the highest point of its motion?

A spring-powered dart gun is un-stretched and has a spring constant 10.0 N/m.The spring is compressed by 8.00 cm and a 5.00 gram projectile is placed in the gun.The kinetic energy of the projectile when it is shot from the gun is

A student lifts a weight of 10.0 N a distance of 0.500 meters.The energy needed to do this work in calories is (1 cal = 4.186 Joules)

A 90.0 kg person is running up the stairs at 0.500 m/s.The power needed to run up the stairs is

A 20.0 kg box slides up a 12.0 m long incline at an angle of 30.0 degrees with the horizontal.A force of 150 N is applied to the box to pull it up the incline.The applied force makes an angle of 0.00 degrees to the incline.If the incline has a coefficient of kinetic friction of 0.100,then the increase in the kinetic energy of the box is

The explosion in a cannon exerts an average force of 30,000 N for L meters,the length of the cannon.The length of the cannon to shoot a 2.00 kg projectile from the cannon on the earth to the moon is

An airplane has a mass of 30,000 kg and travels at 300 m/s.If the drag force is 1000 N,the power the engines have to provide to keep flying at a constant speed is

A 2000 kg car accelerates from rest to a velocity of 20 m/s in 10 seconds.The power of the engine during this acceleration is

A 20.0 kg box slides down a 12.0 m long incline at an angle of 30.0 degrees with the horizontal.A force of 50.0 N is applied to the box to try to pull it up the incline.The applied force makes an angle of 10.00 degrees to the incline and above the incline.If the incline has a coefficient of kinetic friction of 0.100,then the increase in the kinetic energy of the box is

A 2.00 kg pendulum bob on a string 3.00 m long is released with a velocity of 1.00 m/s when the support string makes an angle of 30.0 degrees with the vertical.What is the tension in the string at the highest point of its motion?

A comet is observed to pass 1.50 $\times$ 10⁸ m from the surface of the sun.The sun's radius is 6.96 $\times$ 10⁸ m.What is the speed of the comet at this point,if its speed when passing the Earth's orbit,1.50 $\times$ 10¹¹ m from the sun's center,is 25km/s?

A spring is stretched from its equilibrium position 10 cm when a 1 kg mass is attached to it.Removing the 1 kg mass and replacing it with a 0.50 kg mass then releasing the spring,how high will the 0.50 kg mass rise above the point where it is released?

A 20 N horizontal force is applied to a 4.0 kg box.Friction is negligible.The box moves a horizontal distance of 3.0 meters.The work done by the 20 N force is

A 2.00 kg pendulum bob on a string 1.50 m long,is released with a velocity of 4.00 m/s when the support string makes an angle of 30.0 degrees with the vertical.What is the velocity of the bob at the bottom of the swing?

A dragster drives a quarter mile (402 m)at a constant rate of acceleration,starting from rest and finishing the race at a final speed of 450 km/hr.If the mass of the dragster is 975 kg,together with its driver,and rolling friction is ignored,what average power was developed by the engine,if 50% of the power developed by the engine was delivered to the wheels?

A horizontal force is applied to a 2.0 kg box.The box starts from rest,moves a horizontal distance of 12.0 meters,and obtains a velocity of 8.0 m/s.The change in the kinetic energy is