Question of physics.?

Question

Q.1 .a satellite takes 2hr to complete 1 revolution around the earth with a speed of 31400km/hr . find the radius of the orbit of satellite?

Q.2. two balls of identical shape and size , but of different materials are acted upon by the same force , such that the acceleration of the first ball is only one fourth that of the second ball.calculate the ratio of mass of the first ball with respect to the mass of second ball?

Q.3.a force of 20Newton,acting on a mass of m1produces an acceleration 4m/raise to 2 .the same force when applied to a mass m2 gives it an acceleration of 0.5m/s raise to 2 .what acceleration would the same force produce,when both masses are tied together?

Q.4.a motor cyclist along with the machine is of mass 180kg.while driving at 90km/hr ,he stops his machine over a distance of 10m. calculate the retarding force of the brakes?

Answer 1

1) If the satellite took 2 hrs, then the total distance around was:

31400 km/hr * 2 hr = 62800 km (which is the circumference of the orbit)

Circumference  = 2πr = 62800

r = 62800/(2π) = 10000 km (using π = 3.14)

2) F = m1*a1 = m2*a2

a1 = 1/4 a2

m1 (1/4 a2) = m2*a2

1/4 m1 = m2

4:1 ratio of first ball to second.

3) 20 N = m1(4 m/s²)

m1 = 5 kg

20 N = m2(.5 m/s²)

m2 = 40 kg

F = (m1 + m2)a

20 = (5 + 40)a

a = 20/45 = .444 m/s²

4) V0 (initial velocity) = 90 km/hr

90 km/hr x (1000 m/km) x (1 hr/3600 s) = 25 m/s

V (ending velocity) = V0 + at

0 = 25 + at

a = -25/t

d = V0(t) + 1/2a(t²)

d = V0(t) + 1/2(-25/t)(t²)

10 = 25t - 12.5t

10 = 12.5t

t = .8s

a = -25/.8s = -31.25 m/s²