FA AF AF b AT d Figure 7.4 (Quick Quiz 7.2) A block is pulled by a force in four different directions. In each case, the displacement of the block is to the right and of the san magnitude.

Jack and Jill are pushing a box across a horizontal floor, but in opposite directions. If the box is moving to the left, Jack is pushing left, and Jill is pushing to the right, what are the signs of the work they do on the box? (a)WJackWJack is negative and WJillWJill is positive (b)WJackWJack is positive and WJillWJill is positive(c) WJackWJack is negative and WJillWJill is negative(d) WJackWJack is positive and WJillWJill is 0 (e) WJackWJack is positive and WJillWJill is negative

A particle moves in the x-axis from x = 12.8 m to x = 23.7 m under the influence of a force   where F is expressed in newtons and x is expressed in meters. Use numerical integration to determine the total work done by the force during the displacement. In the networks there are Various calculators for integrals are available.

A nonconstant force is exerted on a particle as it moves in the positive direction along the x axis. The figure below shows a graph of this force F, versus the particle's position x. Find the work done by this force on the particle as the particle moves as follows. Fx (N) 12.0 X (m) 4.0 8.0 12.0 16.0 -12.0 (a) From x; = 0 to x = 8.0 m 44 Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. J (b) From X; = 8.0 to Xf = = 16.0 m |-60 Your response differs from the correct answer by more than 100%. J (c) From x; = 0 to x = 16.0m |-30 The response you submitted has the wrong sign. J