# physics(URGENT!!!!!)

A spherical non-rotating planet (with no atmosphere) has mass m1= 5 ×1024 kg and radius r1= 7000 km. A projectile of mass m2≪m1 is fired from the surface of the planet at a point A with a speed vA at an angle α=30∘ with respect to the radial direction. In its subsequent trajectory the projectile reaches a maximum altitude at point B on the sketch. The distance from the center of the planet to the point B is r2=(5/2)r1. Use G=6.674×10−11 kg−1m3s−2.

What is the initial speed vA of the projectile? (in m/s)

vA=

1. 👍 0
2. 👎 0
3. 👁 228
1. vA=Sqrt(5*G*m1/4*r)=6904.45 m/s

1. 👍 0
2. 👎 0
2. hai Greco A merry-go-round (pictured) is sitting in a playground. It is free to rotate, but is currently stationary. You can model it as a uniform disk of mass 210 kg and radius 120 cm (consider the metal poles to have a negligible mass compared to the merry-go-round). The poles near the edge are 109 cm from the center.

Someone hits one of the poles with a 8 kg sledgehammer moving at 17 m/s in a direction tangent to the edge of the merry-go-round. The hammer is not moving after it hits the merry-go-round.

How much energy |ΔE| is lost in this collision? (enter a positive number for the absolute value in Joules)

|ΔE|= did u got it i need help ???

1. 👍 0
2. 👎 0

1. 👍 0
2. 👎 0
4. Did you do 8b and 8c Greco??

1. 👍 0
2. 👎 0
5. not yet..

1. 👍 0
2. 👎 0
6. Thanks #Greco for nizo ans got it too!!! A ruler stands vertically against a wall. It is given a tiny impulse at θ=0∘ such that it starts falling down under the influence of gravity. You can consider that the initial angular velocity is very small so that ω(θ=0∘)=0. The ruler has mass m= 100 g and length l= 15 cm. Use g=10 m/s2 for the gravitational acceleration, and the ruler has a uniform mass distribution. Note that there is no friction whatsoever in this problem. (See figure)

(a) What is the angular speed of the ruler ω when it is at an angle θ=30∘? (in radians/sec)

ω=

(b) What is the force exerted by the wall on the ruler when it is at an angle θ=30∘? Express your answer as the x component Fx and the y component Fy (in Newton)

Fx=

Fy=

(c) At what angle θ0 will the falling ruler lose contact with the wall? (0≤θ0≤90∘; in degrees) [hint: the ruler loses contact with the wall when the force exerted by the wall on the ruler vanishes.]

θ0= need help for this question i got only omega !

1. 👍 0
2. 👎 0
7. I=1/3*m*L^2
Eini= mg(L/2) + 0
Efin= mg(L/2)cos30 + 1/2*I*w^2
Eini=Efin ->
w=sqrt(3*g (1-cos(theta))/L)

b)
alpha=3*mg/2*sin(theta)/L
ax = -L/2*sin(theta) w^2 + L/2*cos(theta) alpha
Fx=m*ax
Fy=m*g*cos(theta)-m*w^2*(L/2)

c)
cos(theta)=2/3
theta=48.19

1. 👍 0
2. 👎 0

## Similar Questions

1. ### Science

A model shows that the moon has grown to twice its size, yet it has remained in the same place. In one to two sentences, explain how this would impact the gravity between Earth and the moon.(2 points)

2. ### science

if all of the following imaginary planets were the same distance from the sun, which would experience the strongest force of gravity due to the sun? planet a: mass 3,500 kg planet b: mass 50,000 kg planet c: mass 750 kg planet d:

3. ### Science

Scientists have discovered a new planet. The planet is in a solar system whose star is similar in size to the sun and is about as far from the star as Venus is from the sun. The planet is similar in size to Earth, and its

4. ### astronomy

Rank the following hypothetical planets -- all of which have the same total mass and same radius -- from lowest moment of inertia to highest moment of inertia: 1) A uniform sphere of mixed up rock and iron 2) A rocky planet with

1. ### Science

The atmospheres of the planets in our solar system differ in their physical compositions. Which planet would you expect to have the thickest atmosphere? a planet with a hot atmosphere and strong gravity a planet with a cold

2. ### Physics

A planet with mass 7 x 1024 kg orbits a sun with a period of 1 Earth's years. The speed of the planet around that sun is constant and |v|=43000 m/s. What is the mass of that sun?

3. ### Physics

I have a hard time solving this problem. The weight of an object at the surface of a planet is proportional to the planet's mass and inversely proportional to the square of the radius of the planet. Jupiter's radius is 11 times

4. ### Physics

A planet has a mass of 6.22 × 1023 kg and a radius of 2.51 × 106 m. (a) What is the acceleration due to gravity on this planet? (b) How much would a 77.7-kg person weigh on this planet?

1. ### Physics

A planet has a mass of 5.21x10^23 kg and a radius of 2.77x10^6 m. (a) what is the acceleration of this planet? (b) how much would a 65kg person weigh on this planet?

2. ### phy

A satellite circles a spherical planet of unknown mass in a circular orbit of radius 1.9×107m . The magnitude of the gravitational force exerted on the satellite by the planet is 140N . Part A What would be the magnitude of the

3. ### physic

A satellite circles a spherical planet of unknown mass in a circular orbit of radius 1.9×107m . The magnitude of the gravitational force exerted on the satellite by the planet is 140N . What would be the magnitude of the

4. ### physics

As an astronaut, you observe a small planet to be spherical. After landing on thte planet you set off, walking always straight ahead, and find yourself returning to your spacecraft from the opposite side after completing a lap of