When you’re driving on the freeway it’s necessary to keep your foot on the accelerator to keep the car moving at a constant speed. In this situation the net force on the car is zero.
The rate of change of the velocity of a particle with respect to time is called its acceleration. If the velocity of the particle changes at a constant rate, then this rate is called the constant acceleration.
Since we are using metres and seconds as our basic units, we will measure acceleration in metres per second per second. This will be abbreviated as m/s². It is also commonly abbreviated as ms⁻².
For example, if the velocity of a particle moving in a straight line changes uniformly (at a constant rate of change) from 2 m/s to 5 m/s over one second, then its constant acceleration is 3 m/s².
Zero acceleration means constant velocity. Also to be noticed is that the definition of acceleration does not involve any information about forces. Acceleration is a kinematic quantity. Irrespective of what forces are acting, if the velocity is constant, the acceleration is zero.
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Answer:
- Distance between car and the deer when the car stopped = 20 m
- The time required for you to stop once you press the brakes = less than 5 s in order not to hit the deer.
Explanation:
Using the equations of motion,
In the 0.5 s reaction time, we need to first calculate how far he has travelled in that time.
a = 0 m/s² (Since the car is travelling at constant velocity)
x = ?
Initial velocity = u = 20 m/s
x = ut + at²/2
x = 20×0.5 + 0 = 10 m
From that moment,
a = - 10 m/s²
u = initial velocity at the start of the deceleration = 10 m/s
v = final velocity = 0 m/s
x = ?
v² = u² + 2ax
0² = 10² + 2(-10)(x)
20x = 100
x = 5 m
Total distance travelled from when the deer stepped onto the road = 10 + 5 = 15 m
Distance between car and the deer when the car stopped = 35 - 15 = 20 m
b) To determine the time required to stop once you step on the brakes
u = 10 m/s
t = ?
v = 0 m/s²
x = distance from when the brake was stepped on to the deer = 35 - 10 = 25 m
x = (u + v)t/2
25 = (10 + 0)t/2
10t = 50
t = 5 s
Meaning the time required to stop once you step on the brakes is less than 5s.
The frequencies of light that an atom can emit are dependent on states the electrons can be in. When excited, an electron moves to a higher energy level or orbital. When the electron falls back to its ground level the light is emitted.
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Net force on the car=F=4.8 x 10³ N
Explanation:
mass of car= 1.2 x 10³ Kg
initial velocity= Vi=0
Final velocity= Vf= 20 m/s
time = t= 5 s
Using kinematic equation,
Vf= Vi + at
20= 0 + a (5)
5 a=20
a= 20/5
a= 4 m/s²
Now force is given by F = ma
F= 1.2 x 10³ (4)
F=4.8 x 10³ N
When a ray passes from air into glass the direction in which the light ray is travelling changes. The light ray appears to bend as it as it passes through the surface of the glass. ... This 'bending of a ray of light' when it passes from one substance into another substance is called refraction.