The kinetic energy of an object is directly proportional to its mass, and to the square of its velocity.
Answer:
Not the right answer in the options, speed is 4.47 m/s, and the procedure is coherent with option A
Explanation:
Answer A uses mass and velocity units, which are momentum units. By using the conservation of momentum:
.
Since Tom stays in the raft, then both are moving with the same speed. From the options, the momentum is in agreement with option A, however, the question asks for speed.
Answer:
0.29 m
Explanation:
9 mm = 0.009 m in diameter
Cross-sectional area 
Let the tensile modulus of Nickel
.
The elongation of the rod can be calculated using the following formula:

Answer:

Explanation:
Work is given by the equation
where
is force and
is displacement.
Displacement is defined as change in position. In this case, the box moves from 5m to 20m. Its displacement is
.
The force acting on the box is the force of gravity, given as
.
Therefore, the total work done is:
(two significant figures).