#$&* course Phy 121 026. `query 26*********************************************
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Given Solution: `aIf the crate is moving then the force exerted by friction is .30 times the normal force between it and the floor. If the push is horizontal, then the only horizontal forces acting on the crate are the downward force of gravity and the upward force exerted by the floor. Since the crate is not accelerating in the vertical direction, these forces are equal and opposite so the normal force is equal to the weight of the crate. The weight of the crate is 35 kg * 9.8 m/s^2 = 340 N, approx. The frictional force is therefore f = .30 * 340 N = 100 N, approx.. If the crate moves at constant speed, then its acceleration is zero, so the net force acting on it is zero. The floor exerts its normal force upward, which counters the gravitational force (i.e., the weight). The frictional force acts in the direction opposite motion; if net force is zero an equal and opposite force is required, so you must push the box with a force of 100 N in the direction of motion. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Self-critique (if necessary): OK ------------------------------------------------ Self-critique rating #$&* OK "