Answer:
a. 652.68N
b. -2349.65J
c. -3116.12J
d. 5465.77J
e. Zero
Explanation:
a. According to equilibrium of forces, the force of gravity is equal to the sum of the frictional force and force exerted by the man in the opposite direction (since they're both resistant forces).
Fg = Fm + Fr
Fm = Fg - Fr
Fm = mgsin(28°) - umgcos(28°)
u = coefficient of frictional force.
Fm = 330*9.8*sin28 - 0.4*330*9.8*cos28
Fm = 1518.27 - 865.59
Fm = 652.68N
b. Work done by man is:
Wm = -Fm * d
Wm = -652.68 * 3.6
Wm = -2349.65J
c. Work done by friction force:
W(Fr) = -Fr * d
W(Fr) = -865.59 * 3.6
W(Fr) = -3116.12J
d. Work done by gravity:
Wg = Fg * d
Wg = 1518.27 * 3. 6
Wg = 5465.77J
e. Net work done on the piano is:
Work done by friction + work done by gravity + work done by man
= -3116.12 + 5464.77 + (-2349.65)
= 0J
Answer:
It takes 77 N
Explanation:
Using Newton's second law of motion, F=ma (Force equals mass times acceleration. Since the mass of the couch is 385 kg and the target acceleration is 0.2 m/s, you simply multiply mass times acceleration (ma) to get the total force, or 77 N.
Answer:
<em>a. to the west.</em>
Explanation:
An electron in a magnetic field always experience a force that tends to change its direction of motion through the magnetic field. According to Lorentz left hand rule (which is the opposite of Lorentz right hand rule for a positive charge), the left hand is used to represent the motion of an electron in a magnetic field. Hold out the left hand with the fingers held out parallel to the palm, and the thumb held at right angle to the other fingers. If the thumb represents the motion of the electron though the field, and the other fingers represent the direction of the field, then the palm will push in the direction of the force on the particle.
In this case, if we point the thumb (which shows the direction we shot the electron) to the south (towards your body), with the palm (shows the direction of the force) facing up to the roof, then the fingers (the direction of the field) will point west.
Your position at time 
, relative to the stop line:
The Porsche's position:
a. You pass the Porsche immediately after the time it takes for 
:
at which point you both will have traveled 7.8 m from the stop line.
b. The equation in part (a) has two solutions. The Porsche passes you at the second solution of about 
, at which point you both will have traveled 29 m.
c. At time , the Porsche is moving at velocity
so that at the moment it passes you, its speed is 13 m/s, which is about 46.8 km/h and below the speed limit, so neither of you will be pulled over.
