Determine the amount of work required for each of the following:
a) to lower a 35kg sack of rice through a height of 3.5m
b) to carry the 30kg sack of rice 10m along a corridor
c)to crave the sack of rice 15m along the corridor at a constant velocity against a frictional force of 88N
d) to accelerate a 1680kg car from 30km/h to 70km/h against a constant force of air resistance of 750N over a distant of 85m.
Sorry for a lot of questions, I'm just struggling to understand work.
I don't really understand the first two at all, would their be no work? And then for c I guess it's 88x15. Then for d it would be 1380x9.8=FN and FG. The ff would equal 750N but I'm not sure how to find the FA from that information
a. lowering the sack: negative work.
b. horizontal: no work
c. correct
d. on d, you are doing work against friction, AND adding KE to thecar.
Work=friction*distance+1/2 m (vf^2-vi^2)
No problem! I'm here to help you understand the concept of work. Let's go through each question one by one:
a) To lower a 35kg sack of rice through a height of 3.5m: In this case, work is being done against the force of gravity. The formula to calculate work is W = force × distance. Here, the force we need to consider is the weight of the sack of rice, which is the mass (35kg) multiplied by the acceleration due to gravity (9.8m/s^2). So, the work done would be W = (35kg) × (9.8m/s^2) × (3.5m).
b) To carry the 30kg sack of rice 10m along a corridor: In this scenario, no work is being done because the force applied is perpendicular to the direction of motion. The formula W = force × distance implies that if the angle between the force and distance vectors is 90 degrees, the work done is zero. Carrying a sack of rice horizontally doesn't involve overcoming gravity or any other forces in the vertical direction.
c) To move the sack of rice 15m along the corridor at a constant velocity against a frictional force of 88N: In this case, work is being done against the frictional force. Again, using the formula W = force × distance, the work done would be W = (88N) × (15m).
d) To accelerate a 1680kg car from 30km/h to 70km/h against a constant force of air resistance of 750N over a distance of 85m: Here, work is being done against both the force of air resistance and the force required to accelerate the car. First, we need to calculate the force applied to accelerate the car using Newton's second law: F = m × a. In this case, the force applied would be the change in momentum (mass × change in velocity) divided by the time it takes to achieve this change in velocity.
Once we have the force applied, we can calculate the work done against air resistance using the formula W = force × distance. Finally, we add the work done against air resistance to the work done to accelerate the car to get the total work done.
Please note that values for acceleration, air resistance, and other factors may need to be converted to appropriate SI units before calculations.