Force and Work Unit Test
What is the relationship among force, mass, and acceleration?
ANSWER - Force equals mass times acceleration.
Anne exerts a force of 34.1 N to pitch a softball. She moves the ball 1.8 meters before releasing it. What amount of work did Anne do on the ball?
ANSWER - 61.38 J
Which equation can you use to calculate the mechanical advantage of a simple machine?
ANSWER - MA = ^Xi / ^Xo (^ is a triangle)
Harold uses an inclined plane to move a washing machine from the sidewalk into his house. The vertical distance from the sidewalk to the house is 0.8 meters. If the plane has a mechanical advantage of 2.3, how long is the plane?
ANSWER - 0.35 m
Sarah uses an inclined plant to load a chest into her truck. If she does 84 Joules of work, and the inclined plane is 3 meters long, how much force does she expend?
ANSWER - 28 N
Alan will use a compound pulley to lift a crate from the floor of his garage to a storage shelf. The shelf is 3.5 meters above the floor. Alan pulls 10.5 meters of rope to lift the crate. Which statement is correct?
ANSWER - Alan uses one-third the force he would have needed without the compound pulley.
To directly lift a crate 0.6 meters, Joaquin would need to apply 312 newtons of force. Instead, he uses a lever with a mechanical advantage of 3 to lift the crate. How much force does he save by using the lever?
ANSWER - 208 N
Samantha builds a lever to lift objects in a science experiment. The load arm is 0.4 meters. If she wants the lever to have a mechanical advantage of 8, how long should the effort arm be?
ANSWER - 3.2 m
Luisa uses a nutcracker to crack walnuts. She has to squeeze the handles 12 centimeters to crack a walnut. The part of the arms holding the walnut only move 0.3 centimeters. If Luisa applies 21 Newtons of force to crack the walnut, how much force would she need without the nutcracker?
ANSWER - 840 N
Mark needs to clean up a broken glass on the floor. He can use a hand brush or a broom. Why should he choose the broom?
ANSWER - He will use less force with the broom than he would with the brush.
Which statement about simple machines is correct?
ANSWER - Simple machines do not change the amount of work done.
What happens when you use a lever to lift a box?
ANSWER - You use force to transfer mechanical energy into the lever, which transfers the energy to the box.
What is the mathematical representation of a machine’s efficiency?
ANSWER - Efficiency = Eo/Ei 100
Larry uses a lever to lift a box. Where does inefficiency occur in the lever?
ANSWER - where the fulcrum touches the bar
Which is the best statement of the Law of Conservation of Energy?
ANSWER - The amount of energy put out by a simple machine must equal the amount of energy put into the machine.
In 1–2 sentences, explain how to calculate the efficiency of a toaster.
UNGRADED ANSWER - Efficiency equals (useful energy out divided by total energy in) multiplied by 100 to make it a percentage.
A student uses a pulley to lift a log. In 1–2 sentences, explain how she can calculate the pulley’s efficiency.
UNGRADED ANSWER - The equation to find efficiency of pulley equals weight lifted divided by total force multiplied by 100 to get the percent.
In 1–2 sentences, describe an efficient simple machine.
UNGRADED ANSWER - An efficient simple machine is a simple machine that works efficiently.
4 answers
QUESTION 4
Harold uses an inclined plane to move a washing machine from the sidewalk into his house. The vertical distance from the sidewalk to the house is 0.8 meters. If the plane has a mechanical advantage of 2.3, how long is the plane?
ANSWER - 1.84 m
QUESTION 10
Mark needs to clean up a broken glass on the floor. He can use a hand brush or a broom. Why should he choose the broom?
ANSWER - He will apply force to the broom over a shorter distance than he would to the brush.
1 - Force equals mass times acceleration.
2 - 61.38 J
3 - MA = ^Xi / ^Xo (^ is a triangle)
4 - 1.84 m
5 - 28 N
6 - Alan uses one-third the force he would have needed without the compound pulley.
7 - 208 N
8 - 3.2 m
9 - 840 N
10 - He will apply force to the broom over a shorter distance than he would to the brush.
11 - Simple machines do not change the amount of work done.
12 - You use force to transfer mechanical energy into the lever, which transfers the energy to the box.
13 - Efficiency = Eo/Ei 100
14 - where the fulcrum touches the bar
15 - The amount of energy put out by a simple machine must equal the amount of energy put into the machine.
16 17 and 18 do them on your own or later if i remeber and care ill come back telling you what my answers up top got graded but it probably wont be good