3. Reducing friction in a machine
A decreases its actual mechanical advantage
B decreases its work output
C increases its efficiency
D increases its ideal mechanical advantage
4. The efficiency of a machine is always less than 100 percent because
A a machine cannot have an IMA (ideal mechanical advantage) greater than one
B some work is lost to friction
C the work input is too small
D the work output is too great
5. A motor with an efficiency of 75% must supply 240 J of useful work. What amount of work must be supplied to the motor?
A 75 J
B 180 J
C 320 J
D 420 J

What effects result when there is an impact between earth and an asteroid? check all that apply. a.massive flooding. b.extinction of many life forms.c.major earthquakes change in average global temperature.d. giant dust cloud

Astudent throws a water balloon with speed v0 from a height h = 1.76 m at an angle θ = 21° above the horizontal toward a target on the ground. the target is located a horizontal distance d = 9.5 m from the student’s feet. assume that the balloon moves without air resistance. use a cartesian coordinate system with the origin at the balloon's initial position. (a) what is the position vector, rtarge t, that originates from the balloon's original position and terminates at the target? put this in terms of h and d, and represent it as a vector using i and j. (b) in terms of the variables in the problem, determine the time, t, after the launch it takes the balloon to reach the target. your answer should not include h. (c) create an expression for the balloon's vertical position as a function of time, y(t), in terms of t, vo, g, and θ. (d) determine the magnitude of the balloon's initial velocity, v0, in meters per second, by eliminating t from the previous two expressions.

Ashot putter releases the shot some distance above the level ground with a velocity of 12.0 m/s, 51.0 ∘above the horizontal. the shot hits the ground 2.08 s later. you can ignore air resistance. how far did she throw the shot?