Who was the first president to talk to a man on the moon

Which of the following is not a transverse wave? a) soundb) lightc) radiod) all of thesee) none of these

How many neutrons does element x if it’s atomic number is 28 and its mass number is 87

Ahot-air balloon takes off from the ground traveling vertically with a constant upward acceleration of magnitude g/4. after time interval δt, a crew member releases a ballast sandbag from the basket attached to the balloon. how many seconds does it take the sandbag to reach the ground? (express your answer in terms of δt)