Physics Answers

you are explaining to friends why astronauts feel weightless orbiting in the space shuttle, and they respond that they thought gravity was just a lot weaker up there. Convince them and yourself that it isn't so by calculating how much weaker gravity is 250 km

km above the Earth's surface.

Δg/g=?

The space shuttle releases a satellite into a circular orbit 630 km

km above the Earth.

How fast must the shuttle be moving (relative to Earth's center) when the release occurs?

Two objects attract each other gravitationally with a force of 2.0×10⁻¹⁰ N

N when they are 0.22 m

m apart. Their total mass is 4.50 kg

kg . Find their individual masses.

m

mlarger =? msmaller?

2. At a sharp horizontal circular tum a train slows down going from 90.0 km/h to 50.0 km/h in

the 15.0 s it takes to round the bend. The radius of the curve is 150 m. Assume the train

continues to slow down at the same rate. At the moment the train speed reaches 50.0 km/h

calculate:

(a)the magnitude and direction of the tangential acceleration.

(b)the radial acceleration (magnitude and direction).

(c)the magnitude and direction of the total acceleration.

1. A person is jumping from a height ho= 10 m with zero initial velocity and a cricket ball is thrown directly upward with an initial velocity =9.8 m/s at the same instant when time t=0 s as shown in Fig. 1. Consider h=11.5m and i and to be the unit vectors along the X and Y axis. Gravity is acting along the direction and the magnitude of gravitational acceleration is given by g 9.81 m/s². The red dot on the person represents his center of mass.

(a)If the person and the cricket ball consist of a system, find the position and velocity of the center of mass of the system at time t = 0.5 s

(b)If it takes 0.01 seconds for the person to come to complete rest when he hits the ground, calculate the average force acting on the person.

(c)Now consider when the person hits the ground, he bends his knees such that the center of mass of his body is lowered by 15 cm. If the maximum force that the bone of his legs can withstand is 50000 N, will he break his legs?

5. a) Define viscosity.

b) A matter has a body-centered cubic unit cell with a length of 330 𝑝𝑚 along an edge

and a density of 8.57 𝑔 𝑐𝑚−3

. Calculate the atomic mass of the matter.

c) Find the total energy of a moving object of mass 6.3 𝑘𝑔 and momentum

11.5 × 106 𝑘𝑔𝑚𝑠

−1

person is jumping from a height ℎ0 = 10 m with zero initial velocity and a cricket ball is thrown directly upward with an initial velocity 𝑣𝑣0 = 9.8 m/s at the same instant when time t = 0 s as shown in Fig. 1. Consider h = 11.5 m and 𝚤𝚤̂and 𝚥𝚥̂ to be the unit vectors along the X and Y axis. Gravity is acting along the -𝚥𝚥̂direction and the magnitude of gravitational acceleration is given by g = 9.81 m/s2 . The red dot on the person represents his center of mass.

(a) (4 marks) If the person and the cricket ball consist of a system, find the position and velocity of the center of mass of the system at time t = 0.5 s.

(b) (2 marks) If it takes 0.01 seconds for the person to come to complete rest when he hits the ground, calculate the average force acting on the person.

(c) (4 marks) Now consider when the person hits the ground, he bends his knees such that the center of mass of his body is lowered by 15 cm. If the maximum force that the bone of his legs can withstand is 50000 N, will he break his legs?

If the person and the cricket ball consist of a system, find the position and velocity of the center of mass of the system at time t=0.5 s

A proton moving with a velocity of 3×10⁸ ms‐¹ perpendicularly in a magnetic field strength X T. Given that the force of the proton received is 4.8×10‐¹³ N. Find the value of X.

A plane flying due north at 100 m/s is blown by a strong wind at 500 m/s due east. What is the plane's resultant velocity?