We are given information:

If we apply Newton's second law we can calculate acceleration:
F = m * a
a = F / m
a = 25000 / 10000
a = 2.5 m/s^2
Now we can use this information to calculate change of speed.
a = v / t
v = a * t
v = 2.5 * 120
v = 300 m/s
Force is being applied in direction that is opposite to a direction in which space craft is moving. This means that final speed will be reduced.
v = 1200 - 300
v = 900 m/s
Formula for momentum is:
p = m * v
Initial momentum:
p = 10000 * 1200
p = 12 000 000
p = 12 *10^6 kg*m/s
Final momentum:
p = 10000 * 900
p = 9 000 000
p = 9 *10^6 kg*m/s
Answer:
Hence, work done= 287.54 J
Explanation:
Given data:
angle of ramp with the ground θ =20°
force applied = 76 N
work done on the crate to slide down 4 m down the ramp
W= F×d cosθ ( only the cos component of the force will slide the crate down)
W= 76×4×cos20= 287.54 J
Answer:
(a) Steel rod: 
Copper rod: 
(b) Steel rod: 
Copper rod: 
Explanation:
Length of each rod = 0.75 m
Diameter of each rod = 1.50 cm = 0.015 m
Tensile force exerted = 4000 N
(a) Strain is given as the ratio of change in length to the original length of a body. Mathematically, it is given as
Strain = 
where Y = Young modulus
F = Fore applied
A = Cross sectional area
For the steel rod:
Y = 200 000 000 000 
F = 4000N
A =
(r = d/2 = 0.015/2 = 0.0075 m)
=> A = 
=> A = 0.000177 
∴ 
For the copper rod:
Y = 120 000 000 000 N/m²
F = 4000N
A =
(r = d/2 = 0.015/2 = 0.0075 m)
=> A = 
=> A = 0.000177 

(b) We can find the elongation by multiplying the Strain by the original length of the rods:
Elongation = Strain * Length
For the steel rod:
Elongation = 
For the copper rod:
Elongation =
Answer:
457.81 Hz
Explanation:
From the question, it is stated that it is a question under Doppler effect.
As a result, we use this form
fo = (c + vo) / (c - vs) × fs
fo = observed frequency by observer =?
c = speed of sound = 332 m/s
vo = velocity of observer relative to source = 45 m/s
vs = velocity of source relative to observer = - 46 m/s ( it is taking a negative sign because the velocity of the source is in opposite direction to the observer).
fs = frequency of sound wave by source = 459 Hz
By substituting the the values to the equation, we have
fo = (332 + 45) / (332 - (-46)) × 459
fo = (377/ 332 + 46) × 459
fo = (377/ 378) × 459
fo = 0.9974 × 459
fo = 457.81 Hz