one is this: An exceptional standing jump would raise a person 0.8m off the ground. To do this, what force must a 66-kg person exert against the ground? Assume the person crouches a distance of 0.2m prior to jumping, and thus the upward force has this distance to act over before he leaves the ground. The second is this: A box is given a push so that it slides across the floor. How far will it go, given that the coefficient of kinetic friction is 0.20 and the push imparts an initial speed of 4.0 m/s? On the first one, I was thinking something like F=Ma. However, I guess my problem is that there isn't any acceleration when the person is jumping (their initial speed>their final speed (0)). On the second one, I'm pretty much clueless. Please explain these to me.