Quiz 5

A 1.6-kg block slides down a plane (inclined at 25° with the horizontal) at a constant speed of 2.0 m/s. At what rate is the frictional force doing work on the block? 1) +28 W 2) +13 W 3) -13 W 4) -28 W 5) +6.5 W

3) -13 W

A force acting on an object moving along the x axis is given by Fx = (14x - 3.0x2) N where x is in m. How much work is done by this force as the object moves from x = -1 m to x = +2 m? 1) +12 J 2) +28 J 3) +40 J 4) +42 J 5) -28 J

1) +12 J

If = 10, = 15, and a = 130°, determine the scalar product of the two vectors shown. 1) +96 2) -96 3) +51 4) -51 5) -35

1) +96

A block slides on a rough horizontal surface from point A to point B. A force (magnitude P = 2.0 N) acts on the block between A and B, as shown. Points A and B are 1.5 m apart. If the kinetic energies of the block at A and B are 5.0 J and 4.0 J, respectively, how much work is done on the block by the force of friction as the block moves from A to B? 1) -3.3 J 2) +1.3 J 3) +3.3 J 4) -1.3 J 5) +4.6 J

1) -3.3 J

A 3.0-kg block is dragged over a rough horizontal surface by a constant force of 16 N acting at an angle of 37° above the horizontal as shown. The speed of the block increases from 4.0 m/s to 6.0 m/s in a displacement of 5.0 m. What work was done by the friction force during this displacement? 1) -34 J 2) -64 J 3) -30 J 4) -94 J 5) +64 J

1) -34 J

If = 5.0, = 8.0, and a = 30°, determine the scalar product of the two vectors shown. 1) -35 2) +35 3) -20 4) +20 5) +40

1) -35

A 10-kg block on a horizontal frictionless surface is attached to a light spring (force constant = 0.80 kN/m). The block is initially at rest at its equilibrium position when a force (magnitude P = 80 N) acting parallel to the surface is applied to the block, as shown. What is the speed of the block when it is 13 cm from its equilibrium position? 1) 0.85 m/s 2) 0.89 m/s 3) 0.77 m/s 4) 0.64 m/s 5) 0.52 m/s

1) 0.85 m/s

A 1.5-kg object moving along the x axis has a velocity of +4.0 m/s at x = 0. If the only force acting on this object is shown in the figure, what is the kinetic energy of the object at x = +3.0 m? 1) 18 J 2) 21 J 3) 23 J 4) 26 J 5) 8 J

1) 18 J

A 3.0-kg block is on a frictionless horizontal surface. The block is at rest when, at t = 0, a force (magnitude P = 2.0 N) acting at an angle of 22° above the horizontal is applied to the block. At what rate is the force P doing work at t = 2.0 s? 1) 2.3 W 2) 2.0 W 3) 1.4 W 4) 1.7 W 5) 1.2 W

1) 2.3 W

The horizontal surface on which the block slides is frictionless. The speed of the block before it touches the spring is 6.0 m/s. How fast is the block moving at the instant the spring has been compressed 15 cm? k = 2.0 kN/m 1) 3.7 m/s 2) 4.4 m/s 3) 4.9 m/s 4) 5.4 m/s 5) 14 m/s

1) 3.7 m/s

A 2.0-kg block sliding on a frictionless horizontal surface is attached to one end of a horizontal spring (k = 600 N/m) which has its other end fixed. The speed of the block when the spring is extended 20 cm is equal to 3.0 m/s. What is the maximum speed of this block as it oscillates? 1) 4.6 m/s 2) 5.3 m/s 3) 5.7 m/s 4) 4.9 m/s 5) 3.5 m/s

1) 4.6 m/s

The only force acting on a 1.8-kg body as it moves along the x axis is given by Fx = -(3.0x) N, where x is in m. If the velocity of the body at x = 0 is vx = +8.0 m/s, at what value of x will the body have a velocity of +4.0 m/s? 1) 5.7 m 2) 5.4 m 3) 4.8 m 4) 4.1 m 5) 6.6 m

2) 5.4 m

The force an ideal spring exerts on an object is given by Fx = -kx, where x measures the displacement of the object from its equilibrium (x = 0) position. If k = 60 N/m, how much work is done by this force as the object moves from x = -0.20 m to x = 0? 1) -1.2 J 2) +1.2 J 3) +2.4 J 4) -2.4 J 5) +3.6 J

2) +1.2 J

A 2.0-kg block slides down a plane (inclined at 40° with the horizontal) at a constant speed of 5.0 m/s. At what rate is the gravitational force on the block doing work? 1) +98 W 2) +63 W 3) zero 4) +75 W 5) -75 W

2) +63 W

A 2.0-kg projectile moves from its initial position to a point that is displaced 20 m horizontally and 15 m above its initial position. How much work is done by the gravitational force on the projectile? 1) +0.29 kJ 2) -0.29 kJ 3) +30 J 4) -30 J 5) -50 J

2) -0.29 kJ

A 20-kg block on a horizontal surface is attached to a light spring (force constant = 8.0 kN/m). The block is pulled 10 cm to the right from its equilibrium position and released from rest. When the block has moved 2.0 cm toward its equilibrium position, its kinetic energy is 13 J. How much work is done by the frictional force on the block as it moves the 2.0 cm? 1) -2.5 J 2) -1.4 J 3) -3.0 J 4) -1.9 J 5) -14 J

2) -1.4 J

A constant force of 15 N in the negative y direction acts on a particle as it moves from the origin to the point m. How much work is done by the given force during this displacement? 1) +45 J 2) -45 J 3) +30 J 4) -30 J 5) +75 J

2) -45 J

A 6.0-kg block slides along a horizontal surface. If µk = 0.20 for the block and surface, at what rate is the friction force doing work on the block at an instant when its speed is 4.0 m/s? 1) -59 W 2) -47 W 3) -71 W 4) -82 W 5) +71 W

2) -47 W

If vectors and have magnitudes 12 and 15, respectively, and the angle between the two when they are drawn starting from the same point is 110°, what is the scalar product of these two vectors? 1) -76 2) -62 3) -90 4) -47 5) -170

2) -62

How much work is done by a person lifting a 2.0-kg object from the bottom of a well at a constant speed of 2.0 m/s for 5.0 s? 1) 0.22 kJ 2) 0.20 kJ 3) 0.24 kJ 4) 0.27 kJ 5) 0.31 kJ

2) 0.20 kJ

Two vectors and are given by and . If these two vectors are drawn starting at the same point, what is the angle between them? 1) 106° 2) 102° 3) 110° 4) 113° 5) 97°

2) 102°

A 10-kg block on a rough horizontal surface is attached to a light spring (force constant = 1.4 kN/m). The block is pulled 8.0 cm to the right from its equilibrium position and released from rest. The frictional force between the block and surface has a magnitude of 30 N. What is the kinetic energy of the block as it passes through its equilibrium position? 1) 4.5 J 2) 2.1 J 3) 6.9 J 4) 6.6 J 5) 4.9 J

2) 2.1 J

A 2.0-kg body moving along the x axis has a velocity vx = 5.0 m/s at x = 0. The only force acting on the object is given by Fx = (-4.0x) N, where x is in m. For what value of x will this object first come (momentarily) to rest? 1) 4.2 m 2) 3.5 m 3) 5.3 m 4) 6.4 m 5) 5.0 m

2) 3.5 m

The only force acting on a 2.0-kg body moving along the x axis is given by Fx = (2.0x) N, where x is in m. If the velocity of the object at x = 0 is +3.0 m/s, how fast is it moving at x = 2.0 m? 1) 4.2 m/s 2) 3.6 m/s 3) 5.0 m/s 4) 5.8 m/s 5) 2.8 m/s

2) 3.6 m/s

If the vectors and have magnitudes of 10 and 11, respectively, and the scalar product of these two vectors is -100, what is the magnitude of the sum of these two vectors? 1) 6.6 2) 4.6 3) 8.3 4) 9.8 5) 7.6

2) 4.6

A 3.0-kg block is on a horizontal surface. The block is at rest when, at t = 0, a force (magnitude P = 12 N) acting parallel to the surface is applied to the block causing it to accelerate. The coefficient of kinetic friction between the block and the surface is 0.20. At what rate is the force P doing work on the block at t = 2.0 s? 1) 54 W 2) 49 W 3) 44 W 4) 59 W 5) 24 W

2) 49 W

As a 2.0-kg object moves from m to m, the constant resultant force acting on it is equal to N. If the speed of the object at the initial position is 4.0 m/s, what is its kinetic energy at its final position? 1) 62 J 2) 53 J 3) 73 J 4) 86 J 5) 24 J

2) 53 J

If , , and the angle between and (when the two are drawn starting from the same point) is 60°, what is the scalar product of these two vectors? 1) -13 2) +13 3) +37 4) -37 5) 73

3) +37

A constant force of 12 N in the positive x direction acts on a 4.0-kg object as it moves from the origin to the point m. How much work is done by the given force during this displacement? 1) +60 J 2) +84 J 3) +72 J 4) +48 J 5) +57 J

3) +72 J

At what rate is the gravitational force on a 2.0-kg projectile doing work at an instant when the velocity of the projectile is 4.0 m/s directed 30° above the horizontal? 1) +39 W 2) -78 W 3) -39 W 4) +78 W 5) +25 W

3) -39 W

A 4.0-kg block is lowered down a 37° incline a distance of 5.0 m from point A to point B. A horizontal force (F = 10 N) is applied to the block between A and B as shown in the figure. The kinetic energy of the block at A is 10 J and at B it is 20 J. How much work is done on the block by the force of friction between A and B? 1) -58 J 2) -53 J 3) -68 J 4) -63 J 5) -47 J

3) -68 J

A 2.0-kg block slides down a frictionless incline from point A to point B. A force (magnitude P = 3.0 N) acts on the block between A and B, as shown. Points A and B are 2.0 m apart. If the kinetic energy of the block at A is 10 J, what is the kinetic energy of the block at B? 1) 27 J 2) 20 J 3) 24 J 4) 17 J 5) 37 J

3) 24 J

Two vectors and are given by and . The scalar product of and a third vector is -16. The scalar product of and is +18. The z component of is 0. What is the magnitude of ? 1) 7.8 2) 6.4 3) 3.6 4) 5.0 5) 4.8

3) 3.6

The only force acting on a 1.6-kg body as it moves along the x axis is given in the figure. If the velocity of the body at x = 2.0 m is 5.0 m/s, what is its kinetic energy at x = 5.0 m? 1) 52 J 2) 44 J 3) 36 J 4) 60 J 5) 25 J

3) 36 J

A 2.0-kg block situated on a frictionless incline is connected to a light spring (k = 100 N/m), as shown. The block is released from rest when the spring is unstretched. The pulley is frictionless and has negligible mass. What is the speed of the block when it has moved 0.20 m down the plane? 1) 76 cm/s 2) 68 cm/s 3) 60 cm/s 4) 82 cm/s 5) 57 cm/s

3) 60 cm/s

A 10-kg block on a horizontal frictionless surface is attached to a light spring (force constant = 1.2 kN/m). The block is initially at rest at its equilibrium position when a force (magnitude P) acting parallel to the surface is applied to the block, as shown. When the block is 8.0 cm from the equilibrium position, it has a speed of 0.80 m/s. How much work is done on the block by the force P as the block moves the 8.0 cm? 1) 8.3 J 2) 6.4 J 3) 7.0 J 4) 7.7 J 5) 3.9 J

3) 7.0 J

A 5.0-kg object is pulled along a horizontal surface at a constant speed by a 15-N force acting 20° above the horizontal. How much work is done by this force as the object moves 6.0 m? 1) 78 J 2) 82 J 3) 85 J 4) 74 J 5) 43 J

3) 85 J

A 2.5-kg object falls vertically downward in a viscous medium at a constant speed of 2.5 m/s. How much work is done by the force the viscous medium exerts on the object as it falls 80 cm? 1) +2.0 J 2) +20 J 3) -2.0 J 4) -20 J 5) +40 J

4) -20 J

If = 6.0, = 5.0, and a = 40°, determine the scalar product of the two vectors shown. 1) +19 2) +23 3) -19 4) -23 5) +30

4) -23

A body moving along the x axis is acted upon by a force Fx that varies with x as shown. How much work is done by this force as the object moves from x = 1 m to x = 8 m? 1) -2 J 2) -18 J 3) -10 J 4) -26 J 5) +18 J

4) -26 J

If , , and , what is the angle between the two vectors when they are drawn starting from the same point? 1) 118° 2) 107° 3) 112° 4) 103° 5) 77°

4) 103°

If the scalar product of two vectors, and , is equal to -3.5, if , and the angle between the two vectors when they are drawn starting from the same point is equal to 130°, what is the magnitude of ? 1) 2.1 2) 2.5 3) 2.3 4) 2.7 5) 3.1

4) 2.7

Starting from rest at t = 0, a 5.0-kg block is pulled across a horizontal surface by a constant horizontal force having a magnitude of 12 N. If the coefficient of friction between the block and the surface is 0.20, at what rate is the 12-N force doing work at t = 5.0 s? 1) 0.13 kW 2) 0.14 kW 3) 0.12 kW 4) 26 W 5) 12 W

4) 26 W

The only force acting on a 2.0-kg body as it moves along the x axis is given by Fx = (12 - 2.0x) N, where x is in m. The velocity of the body at x = 2.0 m is 5.5i m/s. What is the maximum kinetic energy attained by the body? 1) 36 J 2) 39 J 3) 43 J 4) 46 J 5) 30 J

4) 46 J

The same constant force is used to accelerate two carts of the same mass, initially at rest, on horizontal frictionless tracks. The force is applied to cart A for twice as long a time as it is applied to cart B. The work the force does on A is WA; that on B is WB. Which statement is correct? 1) WA = WB. 2) WA = WB. 3) WA = 2 WB. 4) WA = 4 WB. 5) WB = 2 WA.

4) WA = 4 WB.