Aball is thrown upward with an initial velocity of 48 ft/sec from a height 640ft. it's height h, in feet, after t seconds is given by h(t)= -16t^2 +48t+640. after how long will the ball reach the ground?
the ball will reach the ground in

3. a particle with initial velocity v⃗ 0=(5.85×103m/s)j^ enters a region of uniform electric and magnetic fields. the magnetic field in the region is b⃗ =−(1.35t)k^. you can ignore the weight of the particle. a. calculate the magnitude of the electric field in the region if the particle is to pass through undeflected, for a particle of charge +0.640 nc.