Why is the answer b for this question? i know acceleration should be negative down but i don't know the other two variables.

B  

Explanation:

Displacement, velocity, and acceleration are vectors: they have magnitude and direction.

The convention is that "down" is negative and "up" is positive.

Thus, if an object is higher than when it started, its displacement is positive. If it is lower, the displacement is negative.

If it is still going "up", its velocity is positive. If it is falling, its velocity is negative.

1. Displacement

The formula for vertical displacement is

Δy = v₀t - ½gt²

If v₀ = 30 m/s, t = 2 s, and g = 9.8 m·s⁻², then

2. Velocity

The formula for vertical velocity is

v = v₀ - gt

If v₀ = 30 m/s, t = 2 s, and g = 9.8 m·s⁻², then

3. Acceleration

The  vertical acceleration is always -g = -9.8 m·s⁻².

The direction of the acceleration is down.

The only option with the sequence "up, up, down" is B.

c

explanation:

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg