Physics Work,Power & Energy Level: High School
A women uses a pulley arrangement to lift a heavy crate . She applies a force that is one fourth the weight of the crate , but moves the rope a distance four times the height that the crate is lifted . Is the work done by the women greater than equal to , or less than the work done by the rope on the crate ? Explain .
Physics Work,Power & Energy Level: High School
A skier starts at the top of a ski jump , which is 25.0 m above his landing point on the slope below . The ski jump is assumed to be frictionless .(a) With what velocity will the skier touch the ground ? (use principle of conservation of energy ) .
(b) After landing let us assume that there is some friction on the ground. Use the work-energy principle to calculate the stopping distance of the skier if the coefficient of kinetic friction between the skier and the ground is 0.60 .
Physics Work,Power & Energy Level: High School
A stone of mass 5.0 kg is dropped from height of 2 m above the ground . Neglect the air resistance acting on the stone .(a) Calculate the potential energy , kinetic energy, and the total mechanical energy of the stone at the point of release .
(b) The same at a height of 1.5 m above the ground .
(c) Using the conservation of mechanical energy calculate the speed of the stone just before it strikes the ground . what is the total mechanical energy of the stone in this case ? Does it verify the principle of conservation of energy ?
(d) Calculate the work done by the force of gravity on the stone when it strikes the ground . Does this verify the work –energy theorem ?
Physics Force & Laws Of Motion Level: High School
A engine delivers 30.0 hp (2.24 x 10 ^4 W) to its wheels while moving at 27.0 m/s (about 60 km/hr) . What is the resistive force acting on the auto at that speed ?
Physics Force & Laws Of Motion Level: High School
Hank (mass = 45 Kg ) dove 12 m (40 ft) into 0.32 (12.5 in) of water(a) What was his kinetic energy when he hit the water ?
(b) What was his speed when he hit the water ?(c) What average net force was exerted on him as he stopped ?
Physics Work,Power & Energy Level: High School
A 800 N box is pushed up a 4.0 m incline to a opening 2.0 m above the ground . The process requires 3200 J of work to be done . What is the average friction force along the plane ?
Physics Work,Power & Energy Level: High School
You are to pull a 2100 N sled 8.0 m at a slow speed across the floor by pulling with a force of 350 N on a rope angled at 20 degrees above the horizontal .(a) How much work will you do ?
(b) What work will friction will do ?
Physics Work,Power & Energy Level: High School
You are to pull a 2100 N sled 8.0 m at a slow speed across the floor by pulling with a force of 350 N on a rope angled at 20 degrees above the horizontal .(a) How much work will you do ?
(b) What work will friction will do ?
Physics Work,Power & Energy Level: High School
A cable lifts a 1350 kg elevator at a constant velocity for a distance of 33 m . What is the work done by each of the following ?(a) The tension in the cable
(b) The elevator weight .
Physics Work,Power & Energy Level: High School
The Conservation of Mechanical Energy
The figure at “click here” shows a skateboarder moving at v = 5 m/s along a horizontal section of a track that slanted upward by 48 degree above the horizontal at its end, which is h = 0.46 m above the ground . When she leaves the track , she follows the characteristic path of projectile motion. Ignoring friction and air resistance , find the maximum height H to which she rises above the end of the track .
Physics Work,Power & Energy Level: High School
The Conservation of Mechanical Energy
A gymnist is swinging on a high bar . The distance between his waist and the bar is 1.0 m , as the drawing shows . At the top of the swing his speed is momentarily zero , ignoring friction and treating the gymnist as if all his mass is located at hi waist , find his speed at the bottom of the swing .
Physics Work,Power & Energy Level: High School
A shot putter puts a shot (weight = 72.1 N ) that leaves his hand at distance of 1.62 m above the ground .(a) Find the work done by the gravitational force when the shot has risen to a height of 2.14 m above the ground . include the correct sign for work .
(b) Determine the change (delta PE = PE f – PE o) in the gravitational potential energy of the shot .
Physics Work,Power & Energy Level: High School
The work energy theorem and kinetic energy
A 7430 kg satellite has an elliptical orbit , as in the figure at “click here” . The point on the orbit that is farthest from the earth is called the apogee and is at the far right side of the drawing . The point on the orbit that is closest to the earth is called the perigee and is at the far left side of the figure . Suppose that the speed of the satellite is 2800 m/s at the apogee and 8550 m/s at the perigee .(a) Find the work done by the gravitational force when the satellite moves from the apogee to the perigee .
(b) Find the work done by the gravitational force when the satellite moves from the perigee to the apogee
Physics Work,Power & Energy Level: High School
Work done by a constant force
Physics Work,Power & Energy Level: High School
A bicyclist coasts down a 6.58 degree hill at a steady speed of 5.18 m/s . Assuming a total mass of 83.8 kg (bicycle plus rider) , What must be the cyclist’s power output to climb the same hill at the same speed ?