A 54.0-kg skateboarder starts out with a speed of 1.70 m/s. He does +80.0 J of work on himself by pushing with his feet against the ground. In addition, friction does -265 J of work on him. In both cases, the forces doing the work are nonconservative. The final speed of the skateboarder is 6.00 m/s. (a) Calculate the change (APE = PEf- PEO) in the gravitational potential energy. (b) How much has the vertical height of the skater changed? Is the skater above or below the starting point? O above the starting point O below the starting point Additional Materials eBook

A 0.200-kg particle has a speed of 1.50 m/s at point and kinetic energy of 7.10 J at point B. (a) What is its kinetic energy at ? J (b) What is its speed at B? m/s (c) What is the net work done on the particle by external forces as it moves from J to Ⓡ?

The force required to compress a non-standard spring as a function of displacement from equilibrium x is given by the equation F(x) = ax2 - bx, where a = 45 N/m2, b = 12 N/m, and the positive x direction is in the compression direction of the spring.  Write a general equation in terms of the given variables for the work required to compress this spring from equilibrium to any point xp.   Calculate the work done, in joules, on the spring as it is compressed from x1 = 56 cm to x2 = 84 cm.

A shopper in a supermarket pushes a cart with a force of 41 N directed at an angle of 25° below the horizontal. The force is just sufficient to overcome various frictional forces, so the cart moves at constant speed. (a) Find the work done by the shopper as she moves down a 42.0-m length aisle. Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. J (b) What is the net work done on the cart? Why? This answer has not been graded yet. (c) The shopper goes down the next aisle, pushing horizontally and maintaining the same speed as before. If the work done by frictional forces doesn't change, would the shopper's applied force be larger, smaller, or the same? What about the work done on the cart by the shopper? This answer has not been graded yet.

Suppose a car travels 108 km at a speed of 40.0 m/s, and uses 1.90 gallons of gasoline. Only 30% of the gasoline goes into useful work by the force that keeps the car moving at constant speed despite friction. (The energy content of gasoline is 1.30 x 103 ) per gallon.) (a) What is the force (in N) exerted to keep the car moving at constant speed? (b) If the required force is directly proportional to speed, how many gallons will be used to drive 108 km at a speed of 28.0 m/s? gallons

Starting from rest, a 1.7x104 kg flea springs straight upward. While the flea is pushing off from the ground, the ground exerts an average upward force of 0.35 N on it. This force does 2.7x10-4 J of work on the flea. (a) What is the flea's speed when it leaves the ground? (b) How far upward does the flea move while it is pushing off? Ignore both air resistance and the flea's weight. (a) Number i (b) Number i Units Units

A 1100 kg car drives up a hill that is 16.2m high. During the drive, two nonconservative forces do work on the car: (i) the force of friction, and (ii) the force generated by the car's engine. The work done by friction is −2.91×105J; the work done by the engine is 6.74×105JFind the change in the car's kinetic energy from the bottom of the hill to the top of the hill

The force component along the displacement varies with the magnitude of the displacement, as shown in the graph. Find the work done by the force in the interval from (a) 0 to 0.9 m, (b) 1.0 to 2.0 m, and (c) 2.0 to 3.8 m. (Note: In the last interval the force component is negative, so the work is negative.)

A force given by (6i – 3j) N acts on an object experiencing a displacement given by (3i – j) m.  Determine the work done by the force.

A snowmobile is pulling a sled (m = 380 kg) across the snowy tundra (see the figure below). The snowmobile applies a pulling force of 2480 N at an angle of pulls the sled over a distance of 49.8 m. (a) How much work is done by the snowmobile? 118719.66 J 0° (b) If the sled is also being acted on by a constant kinetic friction force of 240 N and it started from rest, what is the final speed of the sled? 2848.55 X Your response differs significantly from the correct answer. Rework your solution from the beginning and check each step carefully. m/s Need Help? Read It 16° with respect to the ground and