4.1.2 The Work Done by a Constant Force in Two Dimensions Flashcards
The Work Done by a Constant Force in Two Dimensions
- In two dimensions, work is the scalar product of the force applied to an object and the displacement of the object:.
- If the angle q between the force and the displacement is less than 90°, work is positive. If q is greater than 90°, work is negative. If the force and the displacement are perpendicular, no work is done by the force.
- In problems involving work, it is useful to draw force diagrams. Also, be sure to identify the angle between the force and the displacement
A block with a mass of 2 kg is pushed 20 cm at a constant speed up an incline that makes a 40 degree angle with the floor. How much work is done by gravity on the block? Let D be the displacement of the block.
−2.521 J
A box is pulled along the floor at a constant speed by a force, F, that makes a 30 degree angle with the floor. The force of friction, Ff, opposing the motion is 15 N and the box has a mass of 30 kg. Which of the following is the work done by the pulling force, F, as the object is moved 5 meters? let delta x be the displacement in the x-direction
75 J
A 1.5kg block slides at a constant speed down an angle that forms a 35 degree angle with the horizontal. Which of the following is the work done by the force of friction as the block slides 70 cm? let Ff be the force of friction and delta x the displacement of the block down the slide.
−5.90 J
In order to move a block, a pulling force of 120 pounds at an angle of 25 degrees above the horizontal is required. How much work is done by the 120-pound force in order to pull the block 4 feet? Let Fp be the pulling force and delta x the displacement.
434.88 ft-lb
A block is pulled by a rope at a constant speed 60 cm up an incline that makes a 30° angle with the floor. The tension in the rope is 4 N and is parallel to the incline. If the block has a mass of 3 kg, how much work is done by the pulling force on the block?
2.4 J
A rope pulling on a block from the right makes a 15° angle with the horizontal. If the coefficient of friction between the surface and the block is 0.2, how much work is done by the tension in the rope as it moves the block 3.5 meters to the right at constant speed? The mass of the block is 2 kg.
13.02 J
A rope pulling on a block from the right makes an angle B with the horizontal. If the coefficient of friction between the surface and the block is u, how much work is done by the tension in the rope as it moves the block D meters to right at constant speed? Let m be the mass of the block and f the acceleration due to gravity.
Dumg cos B/(usinB + cosB)
Tow ropes are pulling on a box. The first rope is pulling the box from the right and is parallel to the floor. The second rope, pulling from the left, forms a 110 degree angle with the first rope. If the tension in the second rope is 5N and the box moves 3 meters to the left, what is the work done by the second rope on the box? Let FL be the tension in rope pulling from the left and delta x the displacement
5.13 J
A rope that makes a 15 degree angle with the horizontal pulls a block weighing 3N a distance of 10 meters to the right at a constant velocity. The tension in the rope is a 2N force. How much work is done by the rope acting on the block in the horizontal direction? Let Fx be the tension in the rope and delta x be the displacement in the x-direction.
19.32 J
