Work and Energy

An input of 400 W for 3 minutes results in the output of 50,000 J of work by a certain machine. The efficiency of the machine is:

69.4%

A golf ball hits a wall and bounces back at 3/4 the original speed. What part of the original kinetic energy of the ball did it lose in the collision?

7/17

What is the minimum amount of energy required for an 80 kg climber carrying a 20 kg pack to climb Mount Everest 8850 m high?

8.67 MJ

A block-and-tackle system had a mechanical advantage of 8. How large a mass can be raised vertically by a person exerting a force of 100 N?

81.63 kg

A baseball outfielder throws a baseball of mass 0.15 kg at the speed of 40 m/s in initial angle of 30°. What is the kinetic energy of the baseball at the highest point of the trajectory? Ignore air friction.

90 J

A horizontal force of 200 N is applied for 55 kg cart across a 10 m level surface. If the cart accelerates at 2 m/s then what force of friction acts to retarded the motion of the cart

90 N

A horizontal force of 100 N is applied to move a 45 kg cart across a 9 m level surface. What work is done by the 100 N force?

900 J

A worker pushes a sled with a force of 40 N over a level distance of 6m. If a frictional force of 24 N acts on the wheelbarrow in a direction opposite to that of the worker. What net work jane done in the wheelbarrow?

96 J

How much power is theoretically available from a mass flow of 1000 kg/s of water which falls a vertical distance of 100 m?

980 kW

An airliner of mass 100 metric tons takes off and reaches to the altitude of 10 km above ground. What is the increase in its gravitational potential energy?

9800 MJ

Supposed that an object is lifted vertically each of the distances shown below at constant speed, in the time period given. Case I: 2m; 2s Case II: 4m; 1s. In which case is the average power employed greater?

Case II

The unit of power, watt, is the same as which of the following

Joule/second

Which of the following is that form of energy associated with an object's motion?

Kinetic

When an object is dropped from a tower what is the effect of the air is distance as it falls?

None of the above

Which of the following is that form of energy associated with an object's location?

Potential

The rate at which work is done is equivalent to which of the following?

Power

Two blocks are released from the top of a building. One falls straight down while the other slides down a smooth ramp. If all friction is ignored, which one is moving faster when it reaches the bottom?

They both will have the same speed

The quantity of work equal to one joule is also equivalent to which of the following:

Watt.s

A small wagon at constant velocity carries a 200N crate 10m across a level surface. What is the net work done in the process?

Zero

A very light cart holding a 300 N box is moved at constant velocity across a 15 m level surface. What is the net work done in the process?

Zero

The work done by static friction is always

Zero

The dimensional equation for kinetic energy is

[ML2/T2]

A hill is 100 m long and makes an angle of 12° with the horizontal. As a 50 kg jogger runs up the hill, how much work does gravity do on the jogger?

-10,000 J

A 2 kg ball has zero potential and kinetic energy. Maria drops the ball into a 10 m deep well. After the ball comes to a stop in the mud, the sum of its potential and kinetic energy is:

-196 J

A 2 kg ball has zero kinetic and potential energy. Ernie drops the ball into a 10 m deep well. Just before the ball hits the bottom, the sum of its kinetic and potential energy is

0

Are use the rope 2 m long to swing in 10 kg weight around my head. The tension in the rope is 20 N. in half a revolution how much work is done by the rope on weight?

0

How much work is done by a person lifting a 2 kg object from the bottom of a well at a constant speed of 2m/s for 5 s?

0.20 kJ

A 60 g golf ball is dropped from a height of 2 m and rebounds to 1.5 m. How much energy is lost?

0.29 J

A small boat is towed at a constant speed of 2.5 m/s by a towline in which the tension is 250 N. What is the required horsepower?

0.98 hp

An automobile delivers 30 hp to its wheels with moving at a constant speed of 22 m/s. What is the resistance force on the automobile at this speed? (1 hp = 746 watts)

1,020 N

A simple pendulum, 1 m in length, is released from rest when the string is at angle of 35° from the vertical. What is the speed of the suspended mass at the bottom of the swing?

1.88 m/s

An 80,000 kg airliner is flying at 900 km/hr at height of 10 km. What is it's total energy (kinetic + potential)?

10,340 MJ

A polevault or clear is 6 m. With what velocity does he strike the mat in the landing area?

10.8 m/s

A 15 kg crate initially at rest slides down a ramp of 2 m long and an inclined at an angle of 20° with the horizontal. If there is no friction between the ramp surface in the crates what is the kinetic energy of the crate at the bottom of the ramp?

100 J

What is the kinetic energy of a 0 .135 kg baseball thrown at 40 m/s (90mph)?

108 J

What is the kinetic energy of a 0.135 kg baseball at 40 m/s (90 mph)?

108 J

A girl and her bicycle have a total mass of 40 kg. At the top of the hill her speed is 5 m/s. The hill is 10 m high and 100 m long. If the force of friction as she rides down the hill is 20 N, what is her speed at the bottom?

11 m/s

A rock is thrown straight up with an initial velocity of 15 m/s. Ignore energy lost to air friction. How high will the rock rise?

11.5 m

A horse tows a barge in a canal by means of a rope that makes an angle of 15° with the direction of the barge. The tension in the rope is 120 N. How much work is done in moving the barge 1 km?

115.9 kJ

Adisa pulled a 40 N crate up a 5 m inclined plane at a constant velocity. If the angle of the plane is 37° to the horizontal and there is a 10 N force of friction between the crate and the surface. What is the net gain in potential energy of the crate?

120 J

Rupel pushes a box 5 m by applying a 25 N horizontal force. What work does she do?

125 J

An arrow, shot straight up from a crossbow, has an initial velocity of 50 m/s. Ignore energy lost to air friction. How high will the arrow rise?

127.5 m

A 7 kg bowling ball falls from a 2.0 m shelf. Just before hitting the floor, what will be its kinetic energy? (Assume air resistance is negligible)

137 J

Simple pendulum, 2 m in length, is released with a push when the support string is an angle of 25° from the vertical. If the initial speed with a suspended mass is 1.2 m/s when at the release. What is it's speed at the bottom of the swing?

2.3 m/s

A Russian weightlifter is able to life 230 kg. 2 m in 2 s. What is his power output?

2.45 kW

A horizontal force of 200 N is applied to move a 55 kg cart across a 10 m level surface. What is the work done by the 200 N force?

2000 J

Samantha pushes a 50 N crate up a ramp 25.0 m in length and inclined at 10° with the horizontal. What potential energy change does the crate experience?

220 J

A girl and her bicycle have a total mass of 40 kg. At the top of the hill her speed is 5 m/s and her speed doubles as she rides down the hill. The hill is 10 m high and 100 m long. How much kinetic and potential energy is lost to friction?

2420 J

A jet engine developed 100,000 N of thirst in moving an airplane forward at a speed of 900 km/hr. What is the power developed by the engine?

25 MW

A worker pushes a wheelbarrow with the horizontal force of 50 N over a distance of 5 m. What work does the worker do?

250 J

If both the mass and velocity of a ball are tripled, the kinetic energy is increased by a factor of

27

Old Faithful geyser in Yellowstone park, shoots water more or less hourly to a height of 40 m. With what velocity does the water leave the ground?

28.0 m/s

A 3 kg object starting at rest falls to the ground from a height of 10 m. Just before hitting the ground what will be it's kinetic energy?

294 J

A 10.0 kg box starts at rest and slides 3.5 m down a ramp inclined at an angle at 10° with the horizontal. If there is no friction between the ramp surface and crate. What is the velocity of the crate at the bottom of the ramp?

3.5 m/s

A 2 m long simple pendulum is released by a push when the support string is at an angle of 25° from the vertical. If the initial speed of the suspended mass is 1.2 m/s when at the release point, to what maximum angle will it move in the other side?

30°

A professional skier is skiing down a 30° ski slope. Starting from rest, what is the minimum distance along a slope the skier would have to travel to reach a speed of 56 m/s?

320 m

A worker pushes the wheelbarrow with a force of 50 N over a distance of 5 m. If a frictional force of 43 N acts on the wheelbarrow in a direction opposite to that of the worker. What net work is done on the wheelbarrow?

35 J

A 1200 kg automobile moving at 25 m/s has the brakes applied with the deceleration of 8 m/s. How far does the car travel before it stops?

39 m

What is the kinetic energy of a 75 kg sprinter running at 11 m/s?

4.54 kJ

A 20 N crate starting at rest slides down a rough 5.0 m long ramp, inclined at 25° with the horizontal. 20 J of energy is lost to friction. What will be the velocity of the crate at the bottom of the incline?

4.6 m/s

A pile driver drives a post into the ground. The mass of the pile driver is 2500 kg and it is dropped through a height of 8m on each stroke. If the resisting force of the ground is 4,000,000 N. How far is the post driven in on each stroke?

4.9 cm

A 50 N crate is pulled up 5 m inclined plane at constant velocity. If the angle of the plane is 37° to the horizontal and there is a 10 N force of friction between the crate and the surface. What is the force applied on the crate?

40 N

A 1000 kg sports are accelerated from zero to 35 m/s in 7.5 s. What is the average power delivered by the automobile engine?

41.7 kW

Baseball catcher puts but on an exhibition by catching a 150 g ball dropped my helicopter at a height of 101 m. What is the speed of the baseball just before it hits the catchers glove 1 m above the ground?

44.3 m/s

A parachutist of mass 50 kg jumps out of an airplane at a height of 1000 m. The parachute deploys, and she lands on the ground with a velocity of 5 m/s. How much energy was lost to air friction during this jump?

489, 375 J

A speed boat requires 80 kW to move at a constant speed of 15 m/s. What is the resistive force of the water at this speed?

5333 N

A bobsled makes a run down an ice track starting at 150 m vertical distance up the hill. If there is no friction, what is the velocity at the bottom of the hill?

54 m/s

A 600 g object is suspended from the ceiling at the end of a 2 m long string. As this object swings, it has a speed of 4 m/s at the lowest point of its path. What maximum angle does the string make with the vertical?

54°

A 60 kg woman runs up a flight of stairs having a rise of 4 meter in a time of 4.2 seconds. What average power did she supply?

560 W

Water flows over a section of Niagara Falls at a rate of 1,000,200 kg/s and falls 50 m. What is the power wasted by the waterfall?

588 MW

The unit of work, joul, is the same as which of the following?

newton.meter

As an object is lowered into a deep hole in the surface of the earth which of the following must be assumed in regard to it's potential energy?

Decrease

If during a given physical process the only force acting on an object is friction, which of the following must be assumed in regard to the object's kinetic energy?

Decrease

Which of the following is an example of non conservative force?

Friction