Answer:
a=positive
b=0
c=positive
d=negative
Explanation:
a=acceleration depends on the speed and time. if the speed and time are increasing at the same rate, the acceleration value will be positive as the vehicle is speeding up.
b=the speed and time are not increasing, therefore the vehicle is either stationary or travelling at a steady pace.
c=same explanation as a
d=the speed and time are not increasing at the same rate as the speed is decreasing. this means that the car is slowing down
Answer:
The height at which the object is moved is 10 meters.
Explanation:
Given that,
Force acting on the object, W = F = 490 N
The gravitational potential energy, P = 4900 J
We need to find the height at which the object is moved. We know that the gravitational potential energy is possessed due to its position. It is given by :

So, the height at which the object is moved is 10 meters. Hence, this is the required solution.
Answer:
20 m/s
Explanation:
Recall that one of the equations of motions can be written:
v = u + at, (also see attached for reference)
Where,
v = final speed (we are asked to find this)
u = initial speed = 0 (because it starts from rest)
t = time taken = 5s
We simply substitute the given values into the equation:
v = u + at
v = 0 + (4)(5)
v = 20 m/s
Frequency is defined as the number of repetitions of waves occurring in 1 second. The frequency heard by the man as the ambulance move toward him will be greater than 450 Hz.
<h3>
What is the frequency ?</h3>
Frequency is defined as the number of cycles completed in 1 second. Frequency is given by the formula as,

As the formula shows frequency is inversely proportional to the time that shows if the time is decreasing frequency will increase and vice versa.
In the above case, the ambulance is moving toward the men. So that the time to meet up is decreased that's why the frequency will be greater than the initial frequency from the siren.
Hence the frequency heard by the man as the ambulance move toward him will be greater than 450 Hz.
To learn more about frequency refer to the link ;
brainly.com/question/4393505