These stars fuse helium into carbon just like the sun.
Answer:
I think they use it at night because they want to avoid involving themselves in road accident while crossing the street. When there are reflective strips on their clothes, drivers do notice them even at far ends of the street since the strips will reflect the rays from the car lights to the driver,hence, the driver notifies that there is a pedestrian crossing and therefore slows down.
Answer:
a)
b)
c)
d)
e)
Explanation:
Given that:
- initial speed of turntable,
- full speed of rotation,
- time taken to reach full speed from rest,
- final speed after the change,
- no. of revolutions made to reach the new final speed,
(a)
∵ 1 rev = 2π radians
∴ angular speed ω:
where N = angular speed in rpm.
putting the respective values from case 1 we've
(c)
using the equation of motion:
here α is the angular acceleration
(b)
using the equation of motion:
(d)
using equation of motion:
(e)
using the equation of motion:
Complete question is:
A 1200 kg car reaches the top of a 100 m high hill at A with a speed vA. What is the value of vA that will allow the car to coast in neutral so as to just reach the top of the 150 m high hill at B with vB = 0 m/s. Neglect friction.
Answer:
(V_A) = 31.32 m/s
Explanation:
We are given;
car's mass, m = 1200 kg
h_A = 100 m
h_B = 150 m
v_B = 0 m/s
From law of conservation of energy,
the distance from point A to B is;
h = 150m - 100 m = 50 m
From Newton's equations of motion;
v² = u² + 2gh
Thus;
(V_B)² = (V_A)² + (-2gh)
(negative next to g because it's going against gravity)
Thus;
(V_B)² = (V_A)² - (2gh)
Plugging in the relevant values;
0² = (V_A)² - 2(9.81 × 50)
(V_A) = √981
(V_A) = 31.32 m/s