CH. 6 Work and Energy (Quantitative)

What work is required to stretch a spring of spring constant 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretched position is at x = 0.) A) 0.45 J B) 0.80 J C) 1.3 J D) 0.050 J

A) 0.45 J

A 4.00-kg box of fruit slides 8.0 m down a ramp, inclined at 30.0e from the horizontal. If the box slides at a constant velocity of 5.00 m/s, what is the work done by the weight of the box? A) 157 J B) -157 J + 78.4 J C) 78.4 J D) -78.4 J

A) 157 J

A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the 5500 N force? A) 2.75 ̨ 105 J B) -2.45 ̨ 105 J C) 3.00 ̨ 104 J D) -5.20 ̨ 105 J

A) 2.75 ̨ 105 J

A force moves an object in the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 0 to 2.0 m. A) 20 J B) 40 J C) 60 J D) 80 J

A) 20 J

A force moves an object in the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 4.0 to 6.0 m. A) 20 J B) 40 J C) 60 J D) 80 J

A) 20 J

A 30.0-N stone is dropped from a height of 10.0 m, and strikes the ground with a velocity of 7.00 m/s. What average force of air friction acts on it as it falls? A) 22.5 N B) 75.0 N C) 225 N D) 293 N

A) 22.5 N

A spring is characterized by a spring constant of 60 N/m. How much potential energy does it store, when stretched by 1.0 cm? A) 3.0 ̨ 10-3 J B) 0.30 J C) 60 J D) 600 J

A) 3.0 ̨ 10-3 J

A 1.0-kg ball falls to the floor. When it is 0.70 m above the floor, its potential energy exactly equals its kinetic energy. How fast is it moving? A) 3.7 m/s B) 6.9 m/s C) 14 m/s D) 45 m/s

A) 3.7 m/s

A 10-kg mass, hung onto a spring, causes the spring to stretch 2.0 cm. What is the spring constant? A) 4.9 ̨ 103 N/m B) 5.0 ̨ 103 N/m C) 20 N/m D) 2.0 N/m

A) 4.9 ̨ 103 N/m

A 30-N box is pulled 6.0 m up along a 37e inclined plane. What is the work done by the weight (gravitational force) of the box? A) -11 J B) -1.1 ̨ 102J C) -1.4 ̨ 102 J D) -1.8 ̨ 102 J

B) -1.1 ̨ 102J

You lift a 10-N physics book up in the air a distance of 1.0 m, at a constant velocity of 0.50 m/s. What is the work done by the weight of the book? A) +10 J B) -10 J C) +5.0 J D) -5.0 J

B) -10 J

A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the weight of the elevator? A) 2.75 ̨ 105 J B) -2.45 ̨ 105 J C) 3.00 ̨ 104 J D) -5.20 ̨ 105 J

B) -2.45 ̨ 105 J

Calculate the work required to compress an initially uncompressed spring with a spring constant of 25 N/m by 10 cm. A) 0.10 J B) 0.13 J C) 0.17 J D) 0.25 J

B) 0.13 J

A toy rocket, weighing 10 N, blasts straight up from ground level with a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 J. To what vertical height does it rise? A) 1.0 m B) 10 m C) 14 m D) 24 m

B) 10 m

A spring-driven dart gun propels a 10-g dart. It is cocked by exerting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave the gun, assuming the spring has negligible mass? A) 10 m/s B) 14 m/s C) 17 m/s D) 20 m/s

B) 14 m/s

A skier, of mass 40 kg, pushes off the top of a hill with an initial speed of 4.0 m/s. Neglecting friction, how fast will she be moving after dropping 10 m in elevation? A) 7.3 m/s B) 15 m/s C) 49 m/s D) 196 m/s

B) 15 m/s

A 100-N force has a horizontal component of 80 N and a vertical component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, and moves 2.0 m horizontally along the floor. What is the cart's final kinetic energy? A) 200 J B) 160 J C) 120 J D) zero

B) 160 J

A roller coaster starts from rest at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 30 m above the bottom of the dip? A) 14 m/s B) 17 m/s C) 24 m/s D) 30 m/s

B) 17 m/s

An object is lifted vertically 2.0 m and held there. If the object weighs 90 N, how much work was done in lifting it? A) 360 J B) 180 J C) 90 J D) 0 J

B) 180 J

A horizontal force of 200 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final kinetic energy of the cart? A) 1.0 ̨ 103 J B) 2.0 ̨ 103 J C) 2.7 ̨ 103 J D) 4.0 ̨ 103 J

B) 2.0 ̨ 103 J

How many joules of energy are used by a 1.0 hp motor that runs for 1.0 hr? (1 hp = 746 W) A) 3.6 ̨ 103 J B) 2.7 ̨ 106 J C) 4.5 ̨ 104 J D) 4.8 J

B) 2.7 ̨ 106 J

A 60-kg skier starts from rest from the top of a 50-m high slope. What is the speed of the slier on reaching the bottom of the slope? (Neglect friction.) A) 22 m/s B) 31 m/s C) 9.8 m/s D) 41 m/s

B) 31 m/s

A force moves an object in the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 2.0 to 4.0 m. A) 20 J B) 40 J C) 60 J D) 80 J

B) 40 J

A cyclist does work at the rate of 500 W while riding. How much force does her foot push with when she is traveling at 8.0 m/s? A) 31 N B) 63 N C) 80 N D) 4000 N

B) 63 N

At what rate is a 60.0-kg boy using energy when he runs up a flight of stairs 10.0-m high, in 8.00 s? A) 75.0 W B) 735 W C) 4.80 kW D) 48 W

B) 735 W

A 400-N box is pushed up an inclined plane. The plane is 4.0 m long and rises 2.0 m. If the plane is frictionless, how much work was done by the push? A) 1600 J B) 800 J C) 400 J D) 100 J

B) 800 J

A driver, traveling at 22 m/s, slows down her 2000 kg car to stop for a red light. What work is done by the friction force against the wheels? A) -2.2 ̨ 104 J B) -4.4 ̨ 104 J C) -4.84 ̨ 105 J D) -9.68 ̨ 105 J

C) -4.84 ̨ 105 J

A projectile of mass m leaves the ground with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. To what vertical height, relative to its launch point, did it rise? A) 220/(mg) meters B) 120/(mg) meters C) 100/(mg) meters D) Impossible to determine without knowing the angle of launch

C) 100/(mg) meters

A 15.0-kg object is moved from a height of 7.00 m above a floor to a height of 13.0 m above the floor. What is the change in gravitational potential energy? A) zero B) 1030 J C) 1176 J D) 1910 J

C) 1176 J

A roller coaster starts at a point 30 m above the bottom of a dip with a speed of 25 m/s (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 45 m above the bottom of the dip? A) 14 m/s B) 16 m/s C) 18 m/s D) 20 m/s

C) 18 m/s

An arrow of mass 20 g is shot horizontally into a bale of hay, striking the hay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. What is the average stopping force acting on the arrow? A) 45 N B) 90 N C) 180 N D) 360 N

C) 180 N

If it takes 50 m to stop a car initially moving at 25 m/s, what distance is required to stop a car moving at 50 m/s under the same condition? A) 50 m B) 100 m C) 200 m D) 400 m

C) 200 m

A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the net work done on the elevator? A) 2.75 ̨ 105 J B) -2.45 ̨ 105 J C) 3.00 ̨ 104 J D) -5.20 ̨ 105 J

C) 3.00 ̨ 104 J

A 2.0-kg mass is released from rest at the top of a plane inclined at 20e above horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20. What will be the speed of the mass after sliding 4.0 m along the plane? A) 2.2 m/s B) 3.0 m/s C) 3.5 m/s D) 5.2 m/s

C) 3.5 m/s

A 60-kg skier starts from rest from the top of a 50-m high slope. If the work done by friction is -6.0 ̨ 103 J, what is the speed of the skier on reaching the bottom of the slope? A) 17 m/s B) 24 m/s C) 34 m/s D) 31 m/s

C) 34 m/s

The kinetic friction force between a 60.0-kg object and a horizontal surface is 50.0 N. If the initial speed of the object is 25.0 m/s, what distance will it slide before coming to a stop? A) 15.0 m B) 30.0 m C) 375 m D) 750 m

C) 375 m

What is the minimum speed of the ball at the bottom of its swing (point B) in order for it to reach point A, which is 1.0-m above the bottom of the swing? FIGURE 6-3 A) 2.2 m/s B) 3.1 m/s C) 4.4 m/s D) 4.9 m/s

C) 4.4 m/s

An object slides down a frictionless inclined plane. At the bottom, it has a speed of 9.80 m/s. What is the vertical height of the plane? A) 19.6 m B) 9.80 m C) 4.90 m D) 2.45 m

C) 4.90 m

An 800-N box is pushed up an inclined plane. The plane is 4.0 m long and rises 2.0 m. It requires 3200 J of work to get the box to the top of the plane. What was the magnitude of the average friction force on the box? A) 0 N B) non-zero, but less than 400 N C) 400 N D) greater than 400 N

C) 400 N

A 10-N force is needed to move an object with a constant velocity of 5.0 m/s. What power must be delivered to the object by the force? A) 0.50 W B) 1.0 W C) 50 W D) 100 W

C) 50 W

Matthew pulls his little sister Sarah in a sled on an icy surface (assume no friction), with a force of 60.0 N at an angle of 37.0e upward from the horizontal. If he pulls her a distance of 12.0 m, what is the work done by Matthew? A) 185 J B) 433 J C) 575 J D) 720 J

C) 575 J

A horizontal force of 200 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final speed of the cart? A) 73 m/s B) 36 m/s C) 8.5 m/s D) 6.0 m/s

C) 8.5 m/s

A spring with a spring constant of 15 N/m is initially compressed by 3.0 cm. How much work is required to compress the spring an additional 4.0 cm? A) 0.0068 J B) 0.012 J C) 0.024 J D) 0.030 J

D) 0.030 J

A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal spring with spring constant of 2.0 ̨ 106 N/m. What is the maximum compression of the spring? (Neglect the mass of the spring.) A) 0.17 m B) 0.34 m C) 0.51 m D) 0.68 m

D) 0.68 m

A pendulum of length 50 cm is pulled 30 cm away from the vertical axis and released from rest. What will be its speed at the bottom of its swing? A) 0.50 m/s B) 0.79 m/s C) 1.2 m/s D) 1.4 m/s

D) 1.4 m/s

A 10-kg mass is moving with a speed of 5.0 m/s. How much work is required to stop the mass? A) 50 J B) 75 J C) 100 J D) 125 J

D) 125 J

A roller coaster starts with a speed of 5.0 m/s at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 30 m above the bottom of the dip? A) 12 m/s B) 14 m/s C) 16 m/s D) 18 m/s

D) 18 m/s

A 12-kg object is moving on a rough, level surface. It has 24 J of kinetic energy. The friction force on it is a constant 0.50 N. How far will it slide? A) 2.0 m B) 12 m C) 24 m D) 48 m

D) 48 m

A force of 10 N is applied horizontally to a 2.0-kg mass on a level surface. The coefficient of kinetic friction between the mass and the surface is 0.20. If the mass is moved a distance of 10 m, what is the change in its kinetic energy? A) 20 J B) 39 J C) 46 J D) 61 J

D) 61 J

A force moves an object in the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 0 to 6.0 m. A) 20 J B) 40 J C) 60 J D) 80 J

D) 80 J

A 1500-kg car accelerates from 0 to 25 m/s in 7.0 s. What is the average power delivered by the engine? (1 hp = 746 W) A) 60 hp B) 70 hp C) 80 hp D) 90 hp

D) 90 hp