Newton's Laws
A person who weighs 800N steps on a scale on the floor of an elevator. If the elevator accelerates upward at 5m/s2 what will the scale read?
a. 400N
b. 800N
c. 1000N
d. 1200N
d
What is the direction of electric field lines on a positive charge? On a negative charge?
a. Away from a positive charge & towards a negative charge
b. towards a positive charge & away from a negative charge
c. away from both positive & negative charges
d. towards both positive & negative charges
a
What is the equation for torque?
T = r F sin ΞΈ
At earth's surface what is the acceleration of gravity?
9.8 m/s^2
The planet mars exerts a gravitational force Fmars on its moon. The moon has a smaller than Mars and exerts a gravitational force Fmoon on Mars. Which statement is true?
a. Fmars>Fmoon
b. Fmoon>Fmars
c. Fmars=Fmoon
c
What is coulombs law?
F=(kq1q2)/r2
A wheel spinning at 3 m/s uniformly accelerates to 6 m/s in 4 s. Its radius is 20 cm. How far around the wheel will a speck of dust travel during that interval?
A) 6 m B) 18 m C) 9 m D) 30 m E) 12 m
Ans. π = π£ βπ£π π‘ = 6 π π β3 π π 4 π = ΒΎ m/s2 v 2 = vo 2 + 2aοx (6 m/s)2 = (3 m/s)2 + 2(ΒΎ m/s2 )x 36 = 9 + 3/2x 27 = 3/2x 18 m
B) 18 m
A block with a mass of 10kg is traveling at 50m/s when it impacts the ground. From how many meters off the ground was the block dropped?
a. 126m
b. 128m
c. 124m
d. 130m
b. 128
A block is pushed along a horizontal and frictionless surface with a horizontal force that varies as a function of time. At t=3s, the acceleration of the block is 5m/s2 and the force is 15N. What is the mass of the block?
a. 1kg
b. 2kg
c. 3kg
d. 5kg
c
Determine the electrical force of attraction between 2 balloons that are charged with the opposite type, but same quantity of charge. The charge is 6x10-7 C and the distance between the balloons is .5m.
F=1.3x10-2N
A bicycle moves at constant speed over a hill along a smoothly curved surface as shown above. Which of the following best describes the directions of the velocity and the acceleration at the instant it is at the highest position?
A) The velocity is towards the right of the page and the acceleration is towards the top of the page.
B) The velocity is towards the right of the page and the acceleration is towards the bottom of the page.
C) The velocity is towards the right of the page and the acceleration is towards the bottom right of the page
B) The velocity is towards the right of the page and the acceleration is towards the bottom of the page.
A ship of mass m and an initial velocity of v0 is coasting to a stop. The water exerts a drag force on the ship. The drag force is proportional to the velocity:
FD=βkv where the negative sign indicates that the drag force acts in a direction opposite the motion. After the ship has coasted for a time equal to 2/k, how fast (in terms of v0) will the ship be moving?
a. 0.37v0
b. 0.63v0
c. 0.135v0
c. 0.135v0
An artificial satellite of mass m1 = 400 kg orbits the earth at a distance
r = 6.45 x 106 m above the center of the earth. The mass of the earth is m2 = 5.98 x 1024 kg. Find (a) the weight of the satellite and (b) the acceleration due to gravity at this orbital radius.
a. 3835N
Fg=(Gm1m2)/r2
Fg=(6.67x10-11)(400)(5.98x1024)
b. 9.59m/s2
F=ma3835/400
Two point charges, each having a charge of +1C, are 2 meters apart. If the distance between them is doubled, by what factor does the force between them change?
k=9.0Γ109Nβ m2/C2
1/4
explanation:
Fe=kq1q2/r2
rf=2ri
A solid cylinder with diameter 20 cm has an angular velocity of 10 rad/s and angular momentum of 2 kg x m2 /s. What is its mass?
A) 0.1 kg B) 5 kg C) 1 kg D) 10 kg E) 2 kg
10 kg
With what minimum velocity must a rocket be launched from the surface of the moon in order to not fall back down due to the moon's gravity?
The mass of the moon is 7.2β1022kg and its radius is 1.8β106m.
G=6.67β10β11m^2N/kg2
a. 2.3km/s
b. 470m/s
c. 520m/s
d. 1.6km/s
a. 2.3km/s
An elevator cable supports an empty elevator car of mass 300 kg. Determine the tension in the cable when the elevator car is (a) at rest and (b) the car has a downward acceleration of 2.0 m/s2.
a. When the elevator car is at rest, the tension in the cable FT is equal to the weight W of the car:
FT = W = mg = (300 kg)(10 m/s2) = 3000 N.
(b) When the elevator car is being lowered with an acceleration of 2.0 m/s2, the downward weight force is greater than the upward tension force. We can use Newtonβs second law to find the tension in the cable. Choosing the downward direction as positive,
F=MA
(W-FT)=ma
(3000)-(300)(2)
2400N upward
A point charge of magnitude 1.6β10β5C is located 0.01m away from a point charge of magnitude 2β10β5C. What is the electric force between the point charges?
k=9β109Nβ m2C2
28800N
F=9β109β1.6β10β5β2β10β5/0.012
A bowling ball of mass 6.0 kg is released from rest from the top of a slanted roof that is 4,0 m long and angled at 30 degrees. The ball rolls along the roof without slipping. The rotational inertia of a sphere of mass M and radius R about its center of mass is 2/5 MR2.
a) Calculate the force due to friction acting on the ball as it rolls along the roof.
b) Calculate the linear speed of the center of mass of the ball when it reaches the bottom edge of the roof.
a) 8.6 N
b) 5.34 m/s
A 100kg satellite is in a Earth circular orbit with radius 1.2 x 10^7 m.
Find the speed.
5,765 m/s