No. Mechanical energy is not conserved. There's quite a bit of friction on the slide. So some of the potential energy is lost to heat on the way down, and the child arrives at the bottom with hot pants and less kinetic energy than you might expect.
f' = frequency observed by the police car after sound reflected from the vehicle and comes back to police car = 1250 Hz
f = frequency emitted by the police car = 1200 Hz
V = speed of sound = 340 m/s
v = speed of vehicle = ?
frequency observed by the police car is given as
f' = f (V + v)/(V - v)
inserting the values in the above equation
1250 = 1200 (340 + v)/(340 - v)
v = 6.9 m/s
Answer: Contact force
a. Applying break in a vehicle.
d. The speed of ball rolling on ground is reduced
Non contact force
b. A coconut falling from a coconut tree.
c. The planets revolving around the sun.
Explanation:
The contact force is the force which exerts when one object or entity comes in contact with other object or entity. For example, on application of break the vehicle stops, the force is applied on the breaks to stop the vehicle. The ball rolling on the ground the speed reduces so the application of force on the ground also reduces.
The non contact force is the force one object exerts on the other without coming in direct contact with the other object. The force exerted by one object on other due to gravity is a non contact force. The coconut falling on the ground and planets revolving around the sun are examples of non contact force due to gravity.
Impulse = change in momentum = F x dt
Where F is sufficiently large and dt is very small(tending to zero).
Therefore impulse = mass x final velocity - mass x initial velocity
= 975 x 3 - 975 x 0.5
= 2437.5 Kg-m/s.
Hence option C is correct.
