Answer:
22 N upward
Explanation:
From the question,
Applying newton's second law of motion
F = m(v-u)/t....................... Equation 1
Where F = Average force exerted by the ground on the ball, m = mass of the baseball, v = final velocity, u = initial velocity, t = time of contact
Note: Let upward be negative and downward be positive
Given: m = 0.14 kg, v = -1.00 m/s, u = 1.2 m/s, t = 0.014 s
Substitute into equation 1
F = 0.14(-1-1.2)/0.014
F = 0.14(-2.2)/0.014
F = 10(-2.2)
F = -22 N
Note the negative sign shows that the force act upward
Answer:
v₀ = 15 m/s
Explanation:
given,
initial velocity = v₀
down acceleration of rock = 10 m/s²
rock distance
S₄ = 7 x S₁
From kinematic equations
S = v₀ t+0.5 at²
at t = 1 s
S₁ = v₀ (1)+0.5 x 10 x 1²
S₁ = v₀+ 5......(1)
at t = 4 s
S₄ = v₀ (4)+0.5 x 10 x 4²
S₄ = 4 v₀+80.....(2)
from equation (1) and (2)
7( v₀ + 5 ) = 4 v₀ +80
3 v₀ = 80 - 35
3 v₀ = 45
v₀ = 15 m/s
