Answer:
The thrown rock strike 2.42 seconds earlier.
Explanation:
This is an uniformly accelerated motion problem, so in order to find the arrival time we will use the following formula:

So now we have an equation and unkown value.
for the thrown rock

for the dropped rock

solving both equation with the quadratic formula:

we have:
the thrown rock arrives on t=5.4 sec
the dropped rock arrives on t=7.82 sec
so the thrown rock arrives 2.42 seconds earlier (7.82-5.4=2.42)
Answer:
Hence, work done= 287.54 J
Explanation:
Given data:
angle of ramp with the ground θ =20°
force applied = 76 N
work done on the crate to slide down 4 m down the ramp
W= F×d cosθ ( only the cos component of the force will slide the crate down)
W= 76×4×cos20= 287.54 J