Answer:
1920Joules
Explanation:
The formula for calculating the kinetic energy of a body is expressed as;
KE = 1/2 mv²
m isthe mass
V is the speed
For the two masses, the combined KE is expressed as;
KE = 1/2(m1+m2)v²
KE = 1/2(45+15)(8)²
KE = 1/2 * 60 * 64
KE = 30 * 64
KE = 1920J
Hence the combined kinetic energy of the boy and the bicycle is 1920Joules
Given,
Effort force = 120 N
Load force= 1050 N
Mechanical advantage of a pulley is given by the ratio of load force to the effort force.



Therefore, the mechanical advantage of the given pulley is 8.75.
Answer:
81 J.
Explanation:
From the question given above, the following data were obtained:
Specific heat capacity (C) = 0.45 J/gK.
Temperature change (ΔT) = 15 K
Mass = 12 g
Heat required (Q) =?
The heat required to raise the temperature of iron can be obtained as illustrated below:
Q = MCΔT
Q = 12 × 0.45 × 15
Q = 81 J
Therefore, the heat required to raise the temperature of the iron is 81 J.
I am the medium one that in the family
Explanation:
Given that,
Mass if the rock, m = 1 kg
It is suspended from the tip of a horizontal meter stick at the 0-cm mark so that the meter stick barely balances like a seesaw when its fulcrum is at the 12.5-cm mark.
We need to find the mass of the meter stick. The force acting by the stone is
F = 1 × 9.8 = 9.8 N
Let W be the weight of the meter stick. If the net torque is zero on the stick then the stick does not move and it remains in equilibrium condition. So, taking torque about the pivot.

W = 3.266 N
The mass of the meters stick is :

So, the mass of the meter stick is 0.333 kg.