Question

1 An object is thrown vertically upward with an initial speed of 30m/s. after 4s the object is:
A moving down at 20m/s

B. moving up at 9.2 m/s
C. moving up at 9.2m/s
Dat its maximum height
E moving down at 9.2 m/s​

Answer 1

Answer:

Answer: E moving down at 9.2 m/s​

Explanation:

Vertical Launch Upwards

This occurs when an object is launched vertically up without taking into consideration any kind of friction with the air.

If vo is the initial speed, t is the time, and g is the acceleration of gravity, the speed of the object is given by:

$v_f=v_o-g.t$

Considering the positive direction of the speed as upwards, if the speed is negative, it means the object is moving down back to the point where it was launched from.

The object is thrown with an initial speed of vo=30 m/s. Let's calculate its speed at t=4 s:

$v_f=30-9.8\cdot 4$

$v_f=30-39.2=-9.2$

$v_f=-9.2\ m/s$

Since it's negative, the object is coming back down.

Answer: E moving down at 9.2 m/s​