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olya-2409
3 months ago
8

A child runs at speed vc while an adult runs at speed va. if the adult gives the child a head start of distance d, how long will

it take for the adult to catch the child? express your answer in terms of va and vc and
d.
Physics
1 answer:
ValentinkaMS [3.4K]3 months ago
4 0
The child runs at speed vc.
The adult runs at speed va.
<span>The adult allows the child a lead of distance d. 
Speed is calculated by distance divided by time: speed = distance/time.
To find the time it takes for the adult to catch the child, use time = d/v.
</span>Let tc be the child's time and ta the adult's time.
tc = D/vc, with D = D + d, so D + d = tc × vc, therefore D = tc × vc - d.
ta = D/va, where D = ta × va.
Equating both: tc × vc - d = ta × va
Thus, ta = (tc × vc - d) / va
You might be interested in
a 75 kg man is standing at rest on ice while holding a 4kg ball. if the man throws the ball at a velocity of 3.50 m/s forward, w
Keith_Richards [3271]

Answer:

The resulting velocity for him will be 0.187 m/s in reverse direction.

Explanation:

Given:

The mass of the man is, M=75\ kg

The mass of the ball is, m=4\ kg

The initial velocity of the man is, u_m=0\ m/s(rest)

The initial velocity of the ball is, u_b=0\ m/s(rest)

The final velocity of the ball is, v_b=3.50\ m/s

The final velocity of the man is, v_m=?\ m/s

To determine this scenario, we employ the principle of momentum conservation.

This principle states that the total initial momentum equals the total final momentum.

Momentum is calculated by multiplying mass by velocity.

Initial momentum = Initial momentum of the man and the ball

Initial momentum = Mu_m+mu_b=75\times 0+4\times 0 =0\ Nm

Final momentum = Final momentum of the man and the ball

Final momentum = Mv_m+mv_b=75\times v_m+4\times 3.50 =75v_m+14

Hence, the total initial momentum equals the total final momentum

0=75v_m+14\\\\75v_m=-14\\\\v_m=\frac{-14}{75}\\\\v_m=-0.187\ m/s

The negative sign indicates that the man moves backward.

Thus, his final velocity ends up being 0.187 m/s backward.

3 0
2 months ago
Coulomb's law for the magnitude of the force FFF between two particles with charges QQQ and Q′Q′Q^\prime separated by a distance
kicyunya [3294]

Response:

Clarification:

The force between two charges, q₁ and q₂ at a distance d is represented by the formula

F = k q₁ q₂ / d²

Here, the force between charge q₁ = -15 x 10⁻⁹ C and q₃ = 47 x 10⁻⁹ C with distance d = (1.66 - 1.24) = 0.42 mm

k = 1 / (4π x 8.85 x 10⁻¹²)

Substituting the values into the equation

F = 1 / (4π x 8.85 x 10⁻¹²) x -15 x 10⁻⁹ x 47 x 10⁻⁹ / (0.42 x 10⁻³)²

= 9 x 10⁹ x -15 x 10⁻⁹ x 47 x 10⁻⁹ / (0.42 x 10⁻³)²

= 35969.4 x 10⁻³ N.

For the force between charge q₂ = 34.5 x 10⁻⁹ C and q₃ = 47 x 10⁻⁹ C at a distance d = (1.24 - 0) = 1.24 mm.

Substituting the values into the expression

F = 1 / (4π x 8.85 x 10⁻¹²) x 34.5 x 10⁻⁹ x 47 x 10⁻⁹ / (0.42 x 10⁻³)²

= 9 x 10⁹ x -34.5 x 10⁻⁹ x 47 x 10⁻⁹ / (0.42 x 10⁻³)²

= 82729.6 x 10⁻³ N

Both forces direct towards the left (away from the origin, towards the negative x-axis)

Total force = 118699 x 10⁻³

= 118.7 N.

5 0
2 months ago
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