Answer:
a) 37.70 m/s
b)710.6 m/s²
Explanation:
Given that ;
Mass of object = 2 kg
Radius of the motion = 2m
Frequency of motion = 3 rev/s
The formula to apply is;
v= 2πrf   where v is linear speed
v = 2×π×2×3 =12π = 37.70 m/s
Centripetal acceleration is given as;
a= 4×π²×r×f²  
a= 4×π²×2×3²
a=710.6 m/s²
 
        
             
        
        
        
Via half-life equation we have:

Where the initial amount is 50 grams, half-life is 4 minutes, and time elapsed is 12 minutes.  By plugging those values in we get:

There is 6.25 grams left of Ra-229 after 12 minutes.
 
        
             
        
        
        
The answer is 100N. Look up the definition of Newton's third law.
        
             
        
        
        
<span>Assuming the car is travelling in the same direction for the entire hour, the acceleration is zero.</span>
        
             
        
        
        
Answer:
(a) The angle of projection is 63 degree. 
(b) The velocity of projection is 24.5 m/s. 
Explanation:
Height, h = 1 m 
horizontal distance, d = 50 m 
time, t = 4.5 s 
Let the initial velocity is u and the angle is A.
(a) Horizontal distance = horizontal velocity x time
50 = u cos A x 4.5
 u cos A = 11.1 .....(1) 
Use second equation of motion in vertical direction 

Divide (2) by (1) 
tan A = 1.97
A = 63 degree 
(b) Substitute the value of A in equation (2)
u x sin 63 = 21.8 
u = 24.5 m/s