Answer:
A) 199.78 J
B) 9.292x10^14 J
C) 4.2x10^7 m/s
D) 0.65 m
E) 1.13x10^-8 sec
D) 2.94x10^-9 sec
Explanation:
mass of ball = 0.0580 kg
A)
If smashed at v = 83.0 m/s, KE is
KE = 0.5mv^2
= 0.5 x 0.0580 x 83.0^2
= 199.78 J
B) if returned at v = 1.79×10^8 m/s, KE will be
KE = 0.5mv^2
= 0.5 x 0.0580 x (1.79×10^8)^2
= 9.292x10^14 J
C) during Einstein's return, velocity of rabbit relative to players is
Vr = 2.21×108 m/s
Rabbit's velocity relative to ball = 2.21×10^8 - 1.79×10^8
= 4.2x10^7 m/s
D) the rabbit's speed approaches the speed of light so we consider relativistic effect. The rabbit's measured distance is
l = l°( 1 - v^2/c^2)
= 2.5(1 - 2.21/3)
= 2.5 x 0.26
= 0.65 m
E) according to the players, the time taken by the rabbit is
t = d/v = 2.5/ 2.21×10^8
= 1.13x10^-8 sec
F) the time for rabbit as measured by rabbit is relativistic
t = t°( 1 - v^2/c^2)
= 1.13x10^-8 (1 - 2.21/3)
= 1.13x10^-8 x 0.26
= 2.94x10^-9 sec
Answer:
Explanation:
The stored elastic energy in the spring helps the box to rise to a height of .75 m
So stored elastic energy = potential energy attained
1/2 k d² = mgh , k is spring constant , d is compression in spring , m is mass of box , h is height attained .
Putting the values
.5 x 220 x d² = 4 x 9.8 x .75
d² = .2673
d = .517 m
51.7 cm .
Answer: C) velocity is a vector and requires a direction.
Explanation:
In physics, there are two types of quantities:
- scalars: these are quantities that have only a magnitude
- vectors: there are quantities that have both magnitude and direction
As an example, speed is a scalar while velocity is a vector. Therefore, speed has only a magnitude, while velocity has both magnitude and direction: therefore, the difference between the two quantities is that velocity is a vector and requires a direction, as stated in option C.
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.
