When a body moves in a circular path,no work is done by the centripetal force since

Consider a particle on which constant forces $F_{1}=\hat{i}+2 \hat{j}+3 \hat{k} \text{ N}$ and $F_{2}=4 \hat{i}-5 \hat{j}-2 \hat{k} \text{ N}$ act together,resulting in a displacement from position $r_{1}=20 \hat{i}+15 \hat{j} \text{ cm}$ to $r_{2}=7 \hat{k} \text{ cm}$. The total work done on the particle is:

$A$ force $\vec F = 6\hat i + 2\hat j - 3\hat k$ acts on a particle,causing a displacement $\vec d = 2\hat i - 3\hat j + c\hat k$. If the work done during this process is zero,find the value of $c$.

$A$ weightlifter lifts a weight off the ground and holds it up.

$A$ body of mass $m$ is moving in a circle of radius $r$ with a constant speed $u$. The force on the body is $mv^2/r$ and is directed towards the centre. What is the work done by this force in moving the body over half the circumference of the circle?

$A$ particle of mass $m$ is projected at an angle $\alpha$ to the horizontal with initial velocity $u \ m/s$. What is the work done by gravity during the time it reaches its highest point?